GPLv3 allows adding a clause that would force them to change the name if they make changes. If they do it anyway they're in violation of the license, no trademark required.
For those asking, it's in section seven, additional clauses:
Notwithstanding any other provision of this License, for material
you add to a covered work, you may (if authorized by the copyright
holders of that material) supplement the terms of this License with
terms:
[...]
c) Prohibiting misrepresentation of the origin of that material,
or requiring that modified versions of such material be marked in
reasonable ways as different from the original version; or...
> The Coppermine Dev Team requires as additional term of the license Coppermine comes with that modified versions of Coppermine conveyed to others should be marked in a reasonable way. Modified versions mustn't be conveyed to others under the same name as the original Coppermine release. Package name, source code and the output generated by the modified version should make it obvious for potential users that the modified version and the original Coppermine version that the modified version is based upon differ.