Copyright, GPL, History, Licensing, Themes
comments 8

WordPress themes, the GPL and the conundrum of derivative works

Now, I know what some readers may be thinking – ‘not another post on the GPL/theme debate’ – but I could hardly write a blog on WP and legal stuff without considering the issue and I hope there’s a point or two in here that at least some people won’t have read before. And no, I don’t try to assert that there’s a single definitive answer.

Meet ‘theme’

In the beginning (of WordPress that is) there was no separate theming system as we know it today. Rather, the theming system that we now know and love was added in version 1.5 (“Strayhorn”), in February 2005, and has been enhanced numerous times since then.

Today, the humble theme – responsible for the layout, look and feel of a site – is a key and swappable component of virtually every WordPress installation and, as most WordPress users know, for those who don’t wish to develop their own theme there is a dazzling array of readily available themes to choose from.

A handful of Genesis themes at StudioPress

A handful of Genesis themes at StudioPress

Evolution of commercial themes and their licensing

As WordPress became more and more popular and as people began to see and leverage its value, it was inevitable that new business models would emerge. One such business model was the development and sale of premium/commercial themes.

Turning to the topic of licensing (and putting what the GPL may require to one side for now), the owners of such businesses could license their themes:

  • in their entirety under the GPL;
  • partly under the GPL and partly under an alternative licence; or
  • in their entirety under an alternative licence.

Early adopters of full GPL model

In the early days, commercial themes were not licensed under the GPL. That began to change in 2008 when Brian Gardner adopted the full GPL model for his Revolution themes (a good number of which I purchased). I distinctly remember his change in approach. It was a big deal at the time.

Brian Gardner's Revolution themes site, which would later evolve into StudioPress

Brian Gardner’s Revolution themes site, which would later evolve into StudioPress

Many others followed suit, including well-known commercial theme providers like WooThemes, GraphPaperPress and Elegant Themes. At the date of writing this post, the commercial section in the themes directory listed 69 commercial theme providers (a number which does not seem to include all of them) who provide themes that are fully-licensed under the GPL.

Controversy and “GPL non-compliant” models

Not all commercial theme providers applied the GPL to their themes. Some applied their own proprietary licences. This ultimately resulted in an eruption of controversy in certain parts of the WordPress community as to the application of the GPL to WordPress themes. Perhaps the most publicised and memorable instance of this was DIY Themes’ initial proprietary licensing of its Thesis theme. The developer of Thesis disagreed strongly that the GPL required Thesis to be GPL-licensed while Matt Mullenweg and others argued strongly (yet, for the most part, calmly) that the GPL required just that. Fight

The title of a post on TheNextWeb sums up just how heated the debate became: “WordPress and Thesis Go to Battle: Mullenweg May Sue”. Matt even tweeted that he would buy people a GPL’d premium theme instead of their buying Thesis. Chris Pearson and Matt debated the issue on Mixergy, with Mixergy’s owner Andrew Warner doing his best to play the role of mediator. The video of that debate is still available today (the day I write this at least) on TheNextWeb at the link above. Listening to it reveals deeply held views as to which position was correct. Matt’s earlier (and consistently held) positions can also be heard in a video on this topic on Matt Mullenweg: WordPress and the GPL.

On an expansive view of the GPL, which of the three models are considered to be GPL-compliant?

I’ve mentioned three possible licensing models above. Listening to the Pearson/Mullenweg debate might make you think there is only one option: that a WordPress theme, when distributed, needs to be licensed in its entirety under the GPL or will be non-compliant with the GPL conditions applying to WordPress itself. But even on what some would say is an expansive view of the GPL’s requirements, that doesn’t seem to be the case. Enter the Software Freedom Law Center.

Software Freedom Law Center opinion

In 2009 Matt sought a legal opinion on the GPL/theme issue from the Software Freedom Law Center (SFLC). You can find it in his post of 2 July 2009, Themes are GPL, too. Matt summarised the SFLC opinion in one sentence: “PHP in WordPress themes must be GPL, artwork and CSS may be but are not required.”

For me, the essence of the opinion is found in these two paragraphs:

“On the basis of that version of WordPress, and considering those themes [that is, the classic and default themes] as if they had been added to WordPress by a third party, it is our opinion that the themes presented, and any that are substantially similar, contain elements that are derivative works of the WordPress software as well as elements that are potentially separate works. Specifically, the CSS files and material contained in the images directory of the “default” theme are works separate from the WordPress code. On the other hand, the PHP and HTML code that is intermingled with and operated on by PHP the code [sic] derives from the WordPress code.

In conclusion, the WordPress themes supplied contain elements that are derivative of WordPress’s copyrighted code. These themes, being collections of distinct works (images, CSS files, PHP files), need not be GPL-licensed as a whole. Rather, the PHP files are subject to the requirements of the GPL while the images and CSS are not. Third-party developers of such themes may apply restrictive copyrights to these elements if they wish.”

So, if one accepts the SFLC opinion, there are two GPL-compliant licensing models for distributed WordPress themes:

  • licensing a theme in its entirety under the GPL; or
  • applying a “split licence” to the theme (under this licence, the PHP code and integrated HTML are covered by the GPL with the rest of the author-created components (such as the CSS and images) being covered by alternative and usually proprietary terms).

The corollary is that commercial themes that are licensed on an alternative basis are GPL non-compliant.

(The split licensing model is the approach that has been adopted for the vast majority of WordPress themes on ThemeForest (which, for most practical purposes, usually limits use of the theme to one site), despite the fact that it’s now possible for a ThemeForest theme author to apply the GPL to a theme in its entirety. It has also been adopted by a number of other commercial theme providers.)

The million dollar question

But the million dollar question remains: was the SFLC’s conclusion regarding application of the GPL to WordPress themes correct?  How did the SFLC come to the conclusion it did and is it necessarily correct that a premium theme must be at least split-licensed? This is a significant question as it seems that, for many, the SFLC opinion has become something akin to ‘GPL/theme gospel’.

The SFLC’s opinion has been written in fairly approachable and succinct terms that make it easy to read. The cost of such brevity is that it does not address key aspects of applicable copyright law in any detail. Rather, a particular version of applicable law appears to be assumed. This has not been lost on certain sections of the WordPress community. There have been some vocal disagreements with the SFLC opinion.

In discussing this broad question, I’m going to try to unpack things a little so as to put the debate in what I consider to be its correct legal context.

Cart before horse

If we stand back for a moment from the SFLC opinion and consider the debate more broadly, we can see that many discussions and views as to why WordPress themes need to be GPL-licensed (either completely or in part) have launched straight into the question of whether a theme is “derivative of WordPress” or “derived from WordPress” and why, technically, that is believed to be so, without any real discussion of the applicable copyright law and what it means in legal terms for something to be a derivative work (or, in other words, what the legal test for a derivative work is). This, with respect, is to put the cart before the horse. The discussion can become technical, philosophical and/or emotional but without proper appreciation and application of the governing legal principles.

Correct approach

To analyse the situation correctly, I think one needs to identify the relevant area of law, explain the applicable aspects of that law and how they relate to the terms of the GPL, and then apply that law and the terms of the GPL to the issue in question. (Please note that I’m not saying that the SFLC didn’t do this. Their opinion will, in all likelihood, be the output of a longer and more involved analysis behind the scenes.)

Relevant area of lawCopyright-law

The relevant area of law is copyright law. Some have argued that the GPL is (also) contractual but that is unlikely to be the case, at least in common law jurisdictions (see, for example, P Jones The GPL is a License, not a Contract, 3 December 2003; Software Freedom Law Center Guide to GPL Compliance, 2nd Edition, 31 October 2014, pp. 16-17).

So, we’re focusing now on questions of copyright. WordPress, as an overall software program consisting of a set of files (including in my view its default themes which come bundled with it), is a copyright work, either as a complete set of code or as a compilation of component files. The owners of the copyright are numerous.  Ownership does not lie with a single person or entity. It lies with its contributors. (The WordPress Core Contributor Handbook states that, “[a]s a contributor, you retain the copyright to your code, however by submitting it to trac you are releasing it under the GPLv2”.)

Simple summary of applicable aspects of copyright law

It is because WordPress is a copyright work that people need permission to copy it or modify it or distribute it. In many if not most legal systems, these acts are restricted acts that can only be exercised by the copyright owner(s) unless permission is granted allowing these acts to occur (or unless there is a statutory defence to infringement). This is where the GPL comes in. It is the means by which all the component parts of the WordPress software can be licensed under a common licence that allows copying, modification and distribution. In other words, the GPL is the means of granting permission for acts which would otherwise by prohibited as a matter of copyright law.

On a copyright analysis, it is vitally important to appreciate that the freedoms granted by the GPL are only required by people building something that will work as part of, with, or on top of WordPress (such as a theme or plugin) when, in copyright law terms, they are doing a restricted act. The most relevant restricted acts are copying the licensed program or a substantial part of it, modifying it (i.e., creating a derivative work) and distributing it. If a person’s actions do not constitute a restricted act, the person is not constrained by copyright and – significantly – is not bound by the terms of the GPL that require downstream GPL licensing upon distribution or publication of a work that “contains or is derived from the Program or any part of it”.

Copyright-related issues

It follows that the broad copyright-related issues that arise when a person develops a WordPress theme for distribution are (or at least include) these:

1. Does the creation and distribution of the particular WordPress theme involve what copyright law would characterise (by reference to the copyright and GPL’d WordPress software) as one or more restricted acts?

2. If the answer is no, the copyright analysis ceases. But if the answer is yes, is there any defence to what would be an actionable copyright infringement where the theme is developed and distributed without permission from the copyright owners?

3. If the creation and distribution of the WordPress theme does involve a restricted act and there is no defence, permission to undertake the relevant act(s) is required. This, in turn, requires adherence to the GPL and that, in turn, raises the question as to what the GPL requires, in the particular circumstances, as to downstream licensing.

WordPress theme development and restricted acts

As noted above, in many if not most legal systems, restricted acts include copying a substantial part of a work or making a derivative work (a work based on the original work). In the context of WordPress themes and the GPL, most of the argument usually centres on whether a derivative work has been made. This is because the GPL share-alike requirements turn (for the most part) on the existence of a distributed modification/derivative work. (We can put mere copying (of all or a part) of WordPress, without distribution, to one side as the GPL expressly allows this without limitation.)

The derivative work question
Before I get into the guts of this issue, I should note that there is a preliminary question as to whether the GPL’s downstream licensing obligation only applies to “derivative works” in orthodox legal terms as opposed to potentially broader wording in the GPL itself. If a broader test applies, the propagation requirements of the GPL would kick in more easily (making it easier to argue that themes are caught by the GPL), but many commentators consider it reasonably clear (and I tend to agree) that the GPL’s authors were focusing on derivative works in orthodox legal terms. (For a far more erudite discussion of this point, see L Determann’s Dangerous Liaisons – Software Combinations as Derivative Works? – Distribution, Installation, and Execution of Linked Programs under Copyright Law, Commercial Licenses, and the GPL (2006) 21 Berkeley Tech LJ 1421. See also L Rosen Open Source Licensing: Software Freedoms and Intellectual Property Law (2004), chapter 6, page 120.)

If we turn now to the SFLC opinion, how does it deal with the derivative work question? It states in strong terms that at least the PHP components of a theme “are derivative of WordPress” but the analysis appears to be based primarily on a technical linking/interdependence or communication analysis, on the assumption that that is the accepted legal test in this context. This is the point that lies at the heart of the debate, as the legal correctness of this approach to ascertaining whether there is a derivative work (i.e., as a matter of copyright law) is not universally accepted. It has, for example, been strongly debated in both the US and the UK (see, for example, L Rosen’s 2003 article When is one program a “derivative work” of another? and A Katz’s 2007 article GPL – The Linking Debate (available to members of The Society for Computers and Law)).

Those who argue that the above approach doesn’t reflect current (US) copyright law note the statutory definition of “derivative work” and what some courts have said must exist for a work to be derivative of another. 17 USC 106(2) defines “derivative work” as:

“‘derivative work’ is a work based upon one or more preexisting works, such as a translation, musical arrangement, dramatization, fictionalization, motion picture version, sound recording, art reproduction, abridgment, condensation, or any other form in which a work may be recast, transformed, or adapted. A work consisting of editorial revisions, annotations, elaborations, or other modifications, which, as a whole, represent an original work of authorship, is a ‘derivative work’.”

Commentators have observed that “courts have determined that to be derivative, a computer program must be substantially similar and in some form include a portion of the copyrighted work” (M Valimaki’s GNU General Public License and the Distribution of Derivative Works [2005] JILT 6 (2005) at para 3.1).

This “test for derivative work” issue is perhaps the most complex and controversial aspect of the GPL in practice. Developers, affected businesses, their lawyers and interested academics all have and are entitled to their opinions, but there are almost as many opinions as there are theme shops because a range of different arguments can be made (see and compare, for example, Valimaki (cited above), T Gue’s Triggering Infection: Distribution and Derivative Works under the GNU General Public License (2012) (1) Journal of Law, Technology & Policy 95, C Bennett’s WordPress Themes, GPL, and Copyright Case Law post from 2010, and P Enrique’s 2014 piece WordPress is GPL, must your plugin be as well?).

Who is right?

So who is right? Well, I like the words of Van Lindberg in his book Intellectual Property and Open Source: A Practical Guide to Protecting Code (O’Reilly, 2008), a book that Professor Lawrence Lessig has described as “clear, correct and deep”. Van Lindberg says this (I like the honesty of the bit I’ve emphasised):

“… there is a persistent issue that won’t go away – whether linking programs together creates a derivative work. If linking creates a derivative work, the GPL applies to the linked program; otherwise, the GPL doesn’t apply.

In legal practice, this arises as a common concern of clients just getting into open source. This questions is usually phrased as either, ‘Can I load and use a GPL-licensed library without applying the GPL to my application?’ or, ‘Do I have to apply the GPL to my plug-in for a particular program if that program is licensed under the GPL?’

I won’t keep you in suspense; the short answer is that we don’t know. For a longer, perhaps more satisfying answer you can skip to the end of the chapter [where he expresses some opinions], but this is a very complicated question.”

Gue makes a similar comment:

“Commentators diverge widely as to whether dynamic linking creates a derivative work. The inconsistency is so great that one commentator has lamented that ‘there appear to be no definitive answers to the question of what constitutes a derivative work under the GPL, not even from the holders of the license in question.’”

The reason we don’t truly know the answer is that the courts haven’t decided a case that is squarely on point (there are potentially analogous cases, of course, but – as far as I’m aware – no GPL or similar case directly on point).  It is only the courts (in the absence of legislative intervention) that can finally determine the matter. Courts might apply what some might say are orthodox notions of what it means for something to be a derivative work or they might incrementally (some might say dangerously) develop the law on this point but we just don’t know. And even if the courts of one country made a definitive ruling on the point, courts in other countries – where other lawsuits might be commenced – could decide differently. As a result, uncertainty remains.

Don’t assume equivalence

I should make another point, and that is that not all themes (or plugins) are made equal. So far as themes are concerned, we might need to consider different kinds of scenarios, such as:

  • a Thesis-style scenario where, apparently, lines of code were copied directly from WordPress (something I can’t personally confirm);
  • another scenario where someone takes the latest default theme bundled with WordPress (which must be under the GPL) and then modifies it and distributes it; and
  • a more complicated scenario where there is no copying of the GPL’d WordPress code at all (assuming, in practical terms, that that’s possible).

The legal conclusions across these three scenarios could be different. I think we need to recognise that.

To what extent does it really matter?

All the above said, and whilst having reasonable certainty as to the application of the GPL to premium themes is desirable, I suggest that, for practical purposes, it is not by itself decisive as to whether a theme owner may wish to GPL-license (or at least GPL split-license) its theme. In other words, the relevant considerations are not only legal ones. Let me explain.

The core WordPress team confers practical benefits on the providers of full-GPL’d premium themes (e.g., promotional blog posts and a listing in the commercial section of the themes repository) while (at least historically) showing a perhaps surprising level of ‘displeasure’, shall we say, not only towards those who do not release premium themes under a GPL licence at all but also (at one time) to those who only apply a split licence (despite this being consistent with the SFLC opinion). Admittedly some years ago now, that displeasure took the form of, for example, online criticism and rejection of ThemeForest members from a WordCamp (see J Caputo’s Automatically Blackballed and Un-Blackballed).

I think the GPL/theme debate has reached the stage where it’s fair to say that a significant proportion of the WordPress community now frowns upon premium theme providers who either don’t GPL-license at all or (probably to a lesser extent) split-license their themes. That mightn’t be good for business and that, for some, may be the bottom line. For some people, this frowning may be caused by a particular view of what the GPL requires but for others – and I think this is a particularly important point – it may be caused by a recognition of the enormous opportunities that WordPress makes possible and the open source spirit and generosity that pervades much of the WordPress community. I think we’ve reached the stage where, for some people, this is more about a community norm than it is about a strict reading of the GPL (not to mention the tedium of listening to more and more competing GPL arguments when, ultimately, only a court can decide).

The counter-argument to my point above, that not applying the GPL could be bad for business, is that GPL-licensing will encourage on-selling of themes by those who didn’t design them to the detriment of the theme designers. This counter-argument doesn’t appear to carry much weight. It’s true that such activity does occur but, generally, on-sellers cannot provide the support and upgrades that the premium theme developers provide. That is often what people pay for. This is a point that Matt has made repeatedly. At least in my own experience as a purchaser of many premium themes and plugins, I think he’s right.

One last thing…

The GPL/WordPress theme debate has fueled all sorts of comment, discussion and, at times, acrimony. After much of the 2009/2010 debate had aired, Mark Jaquith (a lead WordPress developer) stepped in on 17 July 2010 with Why WordPress Themes are Derivative of WordPress, a post that, at least from a technical perspective, sounded compelling. It certainly made me think and probably resulted in the loss of further brain cells as I tried to assimilate his helpful and well-crafted words into the morass of competing arguments. Mark’s firm view was that themes were derivative of WordPress:

“It is the position of the WordPress core developers that themes cannot be considered wholly original creations even when they don’t copy large sections of code in from WordPress. Theme code necessarily derives from WordPress and thus must be licensed under the GPL if it is distributed.”

I almost fell of my seat, then, when I discovered Enrique’s January 2014 piece WordPress is GPL, must your plugin be as well? In this post, Enrique strongly contests the view that plugins must be GPL’d as well. The only comment  made on the post appears to have been made by Mark Jaquith himself. Assuming the comment is genuine, this is what he said:

“Very well argued. My thinking on this matter has evolved since I wrote my post, 3+ years ago. The thing about the GPL is that it is a legal hack. For it to work, it relies on legal concepts like what constitutes a derivative work. And while some plugins could unambiguously be derivative works, I no longer think they must necessarily be so, and I suspect the majority would not be considered derivative works (by a US court, at least). Same goes with themes with the caveat that themes are more likely to contain code lifted from WordPress, so they might veer towards derivation more often than plugins do.”

I was surprised to read this and it doesn’t mean the issue has gone away but, to me, it speaks of pure honesty and integrity. It recognises that not all themes are created equal. And it recognises the important role that the courts have to play. That’s all I have to say.


  1. Hi Richard,

    A very nice overview of the legal situation in terms of GPL and WordPress themes and plugins. Mark Jaquith moving towards supporting non-GPL use of WordPress has something to do with a change in the community. Most of the big players still left standing (Mark Jaquith, Matt Mullenweg via Automattic, Yoast to name just a few) are now involved in intensely commercial WordPress plays. Each is an investor in the WordPress marketplace.

    Even my own Foliovision now has commercial code for sale (a video player).

    We all have a stake in restricting licenses. Our independence in these discussions is compromised. It’s something like the sixties. The Viet Nam protesters long ago finished in the suburbs and some now even order drone strikes (John Kerry).

  2. Hi Alec. Thanks for your comments. Interesting perspective as to a potential reason for a change in approach but, for my part, I’m not sure that’s the real reason (and it’s only a change on the part of one person). It’s true that Mark, Matt and Yoast are involved in the WordPress marketplace but they have always been strong advocates of the GPL and they still are. If we look at Automattic, it releases (and always has released) a heap of code under the GPL (Jetpack being a prime example). As for Matt, you probably couldn’t find a stronger advocate for the GPL. Turning to Mark, he and his colleagues appear to have released their VelocityPage plugin under the GPL (see see here in the comments). I read Mark’s comments as his having had further time to reflect on the legal complexity of the derivative work question and his realising that, in some instances, things are not necessarily as clear cut as some once thought. I genuinely think that’s commendable. Thanks again for your comments and I hope things are going well for you with Foliovision (great looking video player).

    • Matt Mullenweg uses the GPL as a weapon to advance Automattic. His play works two ways:

      One. Automattic as the whale in the WordPress market benefits from GPL as they can adopt anyone’s code and create their own service or bundle it into Jetpack. Just being able to appropriate code does not benefit smaller agencies (we don’t have the audience reach nor the financial means to put teams of three to untaagle another developer’s code).

      Two. Matt Mullenweg and Automattic have specialised in serviceware. Whether Akismet, Vaultpress, security, related posts, stats, comments: all of Automattic’s precious code (I use precious as containing commercial value) is server side. Hence Automattic shares very little commercial code back with the community. Indeed, Automattic works very hard to take self-standing functionality and turn it into server-based services (related posts, stats, security, comments). There is very little independent and free standing about a WordPress install once you install Jetpack.

      As a final weapon, Automattic/Mullenweg use Jetpack to wipe out competitors. Since “everyone” should be using Jetpack, it’s very easy to take over another plugin silo. Slowly Automattic are trying to take over the entire plugin ecosphere with the unavoidable and ubiquitous Jetpack. It’s a borg philosophy: “You will be assimilated. Resistance is futile.” Microsoft used it with great success in the nineties until they’d reached an apex of marketshare and market resentment. I’m surprised as anyone to see Mullenweg follow in Microsoft’s footsteps but actions speak larger than words.

      Remedies: Mullenweg and Automattic should man up and unbundle Jetpack. Let those serviceware plugins compete on a level playing field. Once this is done Automattic will immediately become less predatory (it’s hard to support and market fifteen different plugins) and will have to focus on their natural core business: high end WordPress development and high traffic WordPress hosting ( If Automattic would focus on those natural markets, balance would return to the WordPress ecosphere.

      Those markets won’t keep Mullenweg a billionaire but a founder’s ranking on the billionaire tables should not be the goal of free software. For perspective, Linus Torvald’s fortune is a little over $100 million.

      What shouldn’t not be Automattic’s business is data aggregation and wiping out the individual WordPress developers and small agencies via bundleware and serviceware. The individual WordPress developers who built and popularised and the rich plugin environment had making Matt Mullenweg a second rate Matt Zuckerberg (Facebook founder) in mind when we spent years of our lives to build a truly independent and free publishing platform.

      PS. Thanks for your kind words about our video player. We’ve been improving video on WordPress for almost five years now.

  3. Pingback: Tackling the Issue of WordPress Derivative Works

  4. In short does this mean that if you create any theme for WordPress it should be licenced under GPL?

  5. Richard Best says

    The view of the Software Freedom Law Center is that at least the PHP and any intermingled HTML needs to be released under the GPL. CSS and images, by contrast, can be but do not need to be. If those latter components are not also released under the GPL, two different sets of licensing rights apply to different components of a theme. This is essentially a strategy to constrain people’s uses of the theme to what is allowed by the non-GPL licensing rights. Not that many theme shops do this. Envato/ThemeForest does but it gives authors/developers the choice to opt for 100% GPL.

    Turning to community norms, and recognising that a norm doesn’t represent the views of outliers, the general trend is to opt for 100% GPL.

    Hope this helps.

  6. Lisa Zirkle says

    I read this piece months ago and came back to read again in light of all that’s been going on the last couple of weeks. As someone who is not new to tech but new to WordPress as a business, I have loved the sharing economy but always been aware there are potential pitfalls. Do I want to be greedy? Or create scarcities where they shouldn’t exist? No, but I also want to make a good living, and now I’m wondering what Matt Mullenweg is about. He has seemed to be earnest in wanting to create opportunities for those who don’t otherwise have them easily — whether it be those who publish for free or very cheaply or those who are providing added value to the WordPress software for a fee. All of that is great, but I hope he realizes his vision may be marred by the heavy handed stance he’s taken with Chris Pearson. It’s also hard to be immune to the diatribe given by James Farmer, and who knows what else will surface. Is it all a smear campaign of Matt by some who may have gotten greedy and who intentionally flouted the GPL? I’m not sure and especially when the SFLC, whom Matt references as the definitive opinion, sees the GPL so broadly with respect to WordPress. I really want to understand and very much appreciate your piece on the GPL muddle, Richard.

  7. Richard Best says

    Hi and thanks Lisa. I’m grateful for your appreciation. Comments like that motivate me to write more. All the best. Richard.

Leave a Reply

Your email address will not be published. Required fields are marked *