master/slave can definitely go - plenty of alternative terms and worth replacing the dated jargon. primary/leader/writer - or something more specific to your domain - all work.
One piece I don't quite get - what does the branch name have to do with that? I always assumed "master" was from audio recording - i.e. a master record. Does that term also have dubious roots?
I think this whole thing has been blown out of context. Master/slave I get, that's a direct correlation to one guy telling everyone else what to do. But the master branch has no say on the other branches. There are no implied slaves or demands.
Going down this road implies any use of the word master in the negative
All that said, I hope they go with trunk. We talk about branches, pruning, and trees yet the "trunk" of the tree is the "master"
The word "master" doesn't even originate from the usage of the word in regards to slavery. This whole thing is just nonsense. If you want to replace master/slave, that makes sense, but it doesn't mean that literally any usage of the word "master" should now be discarded. We still have Masters degrees, for instance.
One piece I don't quite get - what does the branch name have to do with that? I always assumed "master" was from audio recording - i.e. a master record. Does that term also have dubious roots?