As much as I hate sniping but this is a petty way to act as translator. Believe me, I know it's hurt to have someone snipe your work because I had the same experience. But telling someone either to stop translating or join your group is a petty thing to do. Look, if you want to "act professional" project that's abandoned for 2 months with no update will be moved on to new person responsible. Just admit that you take more than what your plate can hold.
After 2 months of no update from your side because you WERE working on it and then released everything fast just because someone else did it was questionable. People, and including me probably think this is not your priority project, which is sad because for some readers this is one of their top fav. You have the audacity to ask someone to stop just because they do something that should be your responsibility. Now act like it is your responsibility, no more excuse. If it were work environment, you could have been dismised already from the project by the higher ups