The OP's tone, seems more of a search for clarification on the legal basis, rather than genuine interest in defending the repo. The legal base (non-existing tr

The OP's tone, seems more of a search for clarification on the legal basis, rather than genuine interest in defending the repo. The legal base (non-existing trademark, so therefore unclear - only based on previous usage) seems foggy and would have to be decided in court. So either you get into an out-of-court agreement, or go to civil court and stand your case. If there's any interest in keeping the name, you should probably just contact a lawyer and clarify with him. But if you don't care, to the point where you can just rename the repo and let the other guy have it (which I'm assuming is the whole point of the letter...) My move would be to keep save your project to a new repo, and just leave and empty readme to keep the name in-use. Even if you don't reply a number of times, that lawyering up (at least to me) looks like a dick scare tactics move...