Question Ulrich asks: “I do theme reviews for the theme repository on WordPress.org. All the code and assets in the theme need to be GPL compatible. I have a few questions about how GPL compatible images work with model releases. The popular GPL compatible image licence is CC0. Can an image be released under CC0 even if there is no model release? Is a CC0 image without a model release GPL compatible? Who is responsible for getting the model release? The photographer, theme author, website owner? Who is liable if a theme with a CC0 image without a model release is used on a pornographic site?” Thanks for the great bunch of questions Ulrich. I appreciate receiving them. Outline and summary Outline Before I jump into the specific questions you’ve raised, I think it may be helpful for some people if we step back from those questions and: sketch out what WordPress.org and the Theme Review Handbook have to say about GPL-compatibility; describe CC0; analyse what is meant by “GPL-compatibility”; and explain why, in my …