IANAL, but simplifying the [what-I-call] legal enumeration, it says: "You must retain, in the Source form of any Derivative Works that You distribute, all copyright notices from the Source form of the Work".
Did you put any copyright notices in your work? If not, it may be too late, because they can continue to distribute the old version that did not have copyright notices.
There's also some requirements that they clearly identify anything they have changed, but I'm guessing they haven't changed much. Maybe their sneaky way of changing the branding would violate this? I don't know, IANAL.
If you believe they have not complied with this part of the license, then what they are doing is no different than hosting your copyrighted movie or book on GitHub and you can send a takedown request, sue for damages, etc. It may not be worth the cost though.