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

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.