Comment by palata
1 month ago
> 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.