If WordPress were a country, our Bill of Rights would be the GPL because it protects our core freedoms. We’ve always done our best to keep WordPress.org clean and only promote things that are completely compatible and legal with WordPress’s license. There have been some questions in the community about whether the GPL applies to themes like we’ve always assumed. To help clarify this point, I reached out to the Software Freedom Law Center, the world’s preeminent experts on the GPL, which spent time with WordPress’s code, community, and provided us with an official legal opinion. One sentence summary: PHP in WordPress themes must be GPL, artwork and CSS may be but are not required.
Lloyd writes at A Fool’s Wisdom that:
Talking about licensing really is the suck. Matt’s article became necessary lately as some commercial theme developers have been very aggressive to WordPress community members, who have shared theme code as allowed by WordPress’s viral GPL v2 license.
It frustrates me when I read commercial theme developers complaining about people “stealing” their themes after the thousands of hours they have worked. They make no mention of the hundreds of thousands of hours others have worked on WordPress (counting on the GPL protecting their freedoms ).
The main point of the legal opinion is that any WordPress theme is so entwined with the main WordPress code as to make it a “derivative work,” and thus subject to WordPress’ copyright and licensing (which is the GPL).
There has been some disagreement in the community about this legal opinion – based on the “viral” nature of the GPL – that WordPress themes also need to be GPL. The main argument against seems to be based on the idea that a WordPress theme could function independently of WordPress. If this were possible, then it would not be an independent work at all.
James Vasile, who wrote the opinion, noted that there might be a situation like this, but that it would be unlikely:
[I]magine using WordPress to serve a single static page. You would use a WordPress theme that does not contain any php but is simply HTML. The HTML would look a lot like data that just passes through the PHP process to the client and does not include any blog entries or sidebar functionality.
It’s a trivial case that turns WordPress into a very complicated version of cat, but that theme would probably be a separate work.
I must say that I find the legal opinion to be strong and defensible, and the alternative opinion – that themes are not derivative works – much less convincing based on current copyright law. Actually, as much as I appreciate the GPL, I do not think this is necessarily correct public policy, even if it works in this specific GPL case (right result, perhaps, wrong policy basis). After all, if WordPress carried a non-GPL, more commercial license, then themes could be banned or controlled in very negative ways – a result I would not appreciate.
To restate again, I think themes would legally be too tied to WordPress and are indeed bound to the GPL – I don’t like the law that makes it so – but I do generally like the GPL (which undermines traditional licensing, but is only powerful because of public-policy problems with the law).
Finally, Mark Ghosh, in an article provocatively titled “Licensing is the vehicle, our users are the environment, writes:
In all of our vacillations, are we getting away from our core philosophies? The freedoms that the GPL and WordPress have offered to the folks who choose to make money from WordPress, are also designed to help another, larger group of people. The people who use the software.