True, I didn't consider that (though there may have been modifications made after the code was copied?). In that case, section 4 would apply, which only requires keeping notices intact, and there aren't any as you said.

It does have this clause:

[...] provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice;

A bit unsure in how that should be taken in this case. There weren't any notices in the fork, and the copyright information is otherwise the same (the LICENSE file). This could also be taken to mean attribution, maybe (since most copyright notices include the author's name), in which case git author info would've probably been enough too.