The EUPL is copyleft for any derivative work (as defined by EU law) so the scope of copyleft is not clearly defined.
But EU law allows linking without producing a derivative work [1] "linking two programs does not produce a single derivative of both (each program stay covered by its primary licence)".
So this is weak copyleft. It's something like LGPL with network protection.
They have modified the EUPL license though, which means they have created another license which is incompatible with EUPL. I believe they should use a different name for the modified license. This is confusing.
> So really it seems this should be considered as licensed as those two.
If you create a different work based on the original (EUPL licensed) work and some AGPL code, you still have to abide by the EUPL but you license the resulting work as AGPL, so others have to abide by the AGPL only.
I'm not a lawyer
[1] https://joinup.ec.europa.eu/collection/eupl/matrix-eupl-comp...