Is WA open source?? Sorry but I've never heard using the word "maintainer" on a proprietary software, only with open source projects. Usually people call themselves "<software> developer" instead.
Our situation is a little unusual in that we didn't participate in the game's creation; Instead, years after the fact, we were entrusted with the source code by the developer company (Team17) so that we could continue maintaining it. The updates are still published by Team17, but almost all programming is done by us. So, I can't think of a more appropriate word.