Not familiar enough with this particular project to know, but a quick glance at the commit log shows some overlap in commit authors, so I guess there is at least some level of sharing happening, probably just not through merges.

But being familiar with this kind of project in general, the branches will probably never be fully merged even in the future, just doesn't make much sense because they are server software targeting very different versions of a game client. There are also two other branches, but they "only" diverged by like one or two thousand commits so far.