Because my FOSS¹ work is mostly WordPress these days, my baseline is the GPL. GPL is far from the only license out there, but — and this is the key point here — it’s widely used and (at least more or less) understood.

The GPL comes with a provision that derived works must also be GPL-licensed², so I spend a certain amount of time hunting down whether some bit of code I want to use can legally be incorporated into such a project. And we do the same thing when reviewing themes: everything that goes in the WordPress.org repository has to be GPL-compatible, so all those nice textures and icons and webfonts that can really make a theme stand out have to be compatible as well.

Note: Compatible.

Not everything in the open-source universe has to be, or should be GPL. But everything that goes into a GPL project has to play well with the GPL.

There are wide swaths of the open-source world for which GPL is too restrictive, and people working in those areas tend to go for permissive licenses like BSD or MIT, or release their work into the public domain outright. And that’s awesome. For some kinds of projects, it’s way more appropriate than a restrictive license. If what you’re releasing is the code equivalent of infrastructure, it will not be useful, and will not spread, with a lot of restrictions on how it can be distributed. Permissive licenses are great for libraries, glue, shims, resets, and all that magic stuff.

Creative Commons — for content, not software — is absolutely one of the more brilliant ideas ever to come along. But remember, there are at least half a dozen such licenses, and they range from totally free, no rights reserved, no restrictions of any kind at all, all the way up to You Can’t Touch This³.  Occasionally people pop up in the theme review mailing list or IRC channel and ask “is a CC license okay”; much more often, people put things out there that just say “CC licensed”, which isn’t properly licensed at all. If anyone’s going to use the stuff, we need to know which rights you’re actually licensing.

Free-as-in-speech fonts finally seem to be standardizing more and more on the SIL Open Font License, no doubt thanks to the runaway success of Google Webfonts; the move to standardization makes things nice and easy. It’s also a nice license: quite permissive and GPL-compatible, and designed for the way fonts are actually built and used.

Notice that the above licenses are really far apart in what they allow, and (free software being chock full o’ free software people as it is) we occasionally have full-scale wars about which one is better. But also notice one similarity: they’re all well-known, widely used, documented. They’re suited to particular purposes: If you want your code used absolutely everywhere without any barriers, use a permissive license; if you want to spread the free software gospel, copyleft. The common licenses are standards, in a way. I know without having to put my project aside for a side trip to the local law library that I can incorporate MIT-licensed code in a GPL project, and also that I can’t do the same if I’m going the other direction. I know that I can package up a theme with a CC-0 photo, but not with one that’s CC-BY-NC-ND.

And ultimately, I don’t care all that much which one you choose — I’ll give you the benefit of the doubt and assume that you chose the path you did for reasons that you knew and fully understood at the time. I just want you to choose a path that allows me to understand how I can and can’t use this thing.

But instead, I keep seeing handmade and non-standard things like⁴ :

License:
– you can freely use it
– you can freely distribute sourcecode
– you can freely modify it as long as you leave my copyright/author info in source code
– if you developing closesource application, you should add my name at least to “about” page of your web application
– if you create an amazing modification, please contact me… I can publish link to your webpage if you’re interested…
– if you want to use my script in commercial application for earning money, you should make a donation to me first

Or⁵ this one:

– All themes are free to use as long as you leave the credits links unchanged in footer.
– You cannot claim our themes or modifications of these themes as yours.
– You cannot modify our themes and distribute them on your website.
– You cannot sell our themes for others.
– We does not allow you to use our themes for websites or individuals that participate in warez, hacking, cracking, malicious computer crime or fraud, or any other material or activity that is illegal.
– We does not allow you to use our themes for websites or individuals that participate in porn, gambling, poker, insurance, forex….

And here’s the thing. After seeing untold dozens of such licenses, I don’t even bother to study them and puzzle out if they’re maybe possibly compatible any more. If the developers actually wanted their stuff to be used, they would’ve made it so, and saved themselves a lot of time thinking about exactly which page a linkback needs to be on, or what list of industries they find too icky. Having actually read a bunch of these, they’re never okay to use in projects or put in the repository, and in the current climate, there is always another library or another template out there. Always.

(And on a personal note, for doG’s sake, please don’t call your homegrown terms a EULA. That does not impress or inspire. It just makes me think of 50-page-long click-through legalese from Sony or iTunes.)