Probably not even releasing the actual source code but some of the tweaks only so he is the one that knows the sacred secrets lol. Later fooling everyone they make some mistake when compiling, it works perfectly on his side.
Seen this kind of crap happening, some chucklefuck takes over/hijacks a project, slaps his name in or renames the core completely like it’s their own, with a common motivation which usually is profit from another person’s work. And this usually kills the project for good. And the funny thing is they don’t have a clue wtf they doing.