It looks like they've squashed everything into a single commit, since there's only a commit on their repo right now that was pushed 28 minutes ago (as of this comment).
That's probably the right thing to do Git-wise, because licences might not be retroactive.
They've squashed the history to hide their earlier "error". This isn't compliant with section 5a of the GPLv3[1].
"sketchy at best" is a polite description of this pattern of behaviour.
[1] https://www.gnu.org/licenses/gpl-3.0.en.html#section5