Comment by mschae23
1 month ago
The EUPL is a fine license, especially if your goal is wide compatibility with other copyleft licenses. However, that compatibility also weakens its own copyleft, which could be surprising if you just read the main text.
Also, the GPL is not as short and has more explicit wording for how it behaves in common situations (like the P2P copying stuff, for example), and it allows certain additional restrictions and exceptions (like what the LGPL is). It's just more well thought-out in my opinion.
Edit: Reading it again, I also just remembered that the EUPL's warranty disclaimer is a lot weaker than usual licenses, and weirdly also asserts the program is a “work in progress”.
> However, that compatibility also weakens its own copyleft
Keep in mind that within EU the GPL's copyleft is as strong as EUPL's or LGPL while at the same time EUPL takes into account network access like AGPL. In practice though, software is distributed outside of the EU and while GPL relies on local laws to "maximize" its copyleftness, EUPL specifically refers to either the EU country of the developer or Belgium if the developers from outside the EU, where the laws do not distinguish between static or dynamic linking (check "More details on the case of linking" from [0] about license compatibility). Also FWIW while FSF suggests that "license hopping" (i.e. changing to some compatible licenses from EUPL to something else) weakens the copyleft, a European Commision lawyer who worked on EUPL has commented doing so would be copyright infringement because the purpose of the compatibility list in EUPL is for interoperability (so that multiple projects with different licenses can coexist) and the purpose would matter in court.
Though in practice since software is often distributed outside of EU, e.g. to US where (it seems) such distinction does exist, people do respect (L)GPL's dynamic vs static linking requirements and from a worldwide perspective EUPL is something like LGPL with a dash of AGPL (making some program functionality available even remotely is considered as distribution). Or in other words, EUPL is basically AGPL within the limitations of EU law.
[0] https://interoperable-europe.ec.europa.eu/collection/eupl/li...
> However, that compatibility also weakens its own copyleft
Can you elaborate on that?
My understanding is that EUPL is a bit like MPLv2 or LGPL in the spirit. Like it protects the project itself, but doesn't go viral like the GPL.
That depends on your interpretation of what a “derivative work” constitutes, which the EUPL delegates to copyright law. For the GPL, it includes other programs linked to the work (which is how it affects other projects using the work as a library). If this definition held true for the EUPL as well, it would behave the same way. (By the way, I don't really like describing copyleft as “viral”, because that implies the GPL (and similar licenses) are like infectious diseases.)
However, the compatibility clause allows relicensing to other licenses that are explicitly weaker in their copyleft, which is what I meant with the quoted sentence.
Another comment just made me aware though that apparently, copyleft extending to other programs linking with the work is just not a thing in the EU? I'll have to read more into the details of that.