In the past year or so there has been a lot of talk about “premium” WordPress themes and plugins, and the GPL. There have been many arguments over whether or not plugins and themes should be able to be licensed under other, non-GPL, licenses. The short answer is yes, they can.
I’m getting tired of the discussions. Plugins for WordPress are GPL because WordPress IS GPL, there’s no question about it being otherwise.
Actually, if you look at the plugin repository guidelines, they only require that a plugin be “GPL-compatible.” The page links to a list of alternate licenses, many of which are compatible with the GPL. And that’s just to get into the repository….
Things really get interesting if you look at the GPL license in the WordPress Codex:
If identifiable sections of that work are not derived from the Program,
and can be reasonably considered independent and separate works in
themselves, then this License, and its terms, do not apply to those
sections when you distribute them as separate works.Â But when you
distribute the same sections as part of a whole which is a work based
on the Program, the distribution of the whole must be on the terms of
this License, whose permissions for other licensees extend to the
entire whole, and thus to each and every part regardless of who wrote it.
If I understand that correctly, the GPL is saying that the parts of a given script that are obviously independant from the main part are considered separate works, and don’t have to be licensed under the GPL unless distributed with the whole. That would mean a plugin would be a separate work, and would only have to be licensed under the GPL if it was distributed with WordPress itself.
Think about it. Is a plugin really a derivative of WordPress, in a GPL sense? A plugin is not distributed with WordPress, it is a separate entity that hooks into WordPress. Saying that “all WordPress must be GPL” is like saying that you can’t have commercial Linux software because they make use of the Linux kernel, which is licensed under the GPL.
Of course, Mullenweg and company still have a right to deny non-GPL-compatible plugins from entering the repository, and I don’t see anything wrong with that.