If I am not mistaken the EUPL is copyleft and inspired by GPL.

In the case here it's however about AGPL. AGPL has the extra thing, that source has to be given not only to somebody who received the software, but also to ones who access it as service via network. (There is some legal debate on the exact details) EUPL afaik doesn't have such a clause, but it's relevant for somebody who builds a "service" and wants to prevent others from running a private fork of it.