It shouldn't be a problem to run mumble concurrently, but like @fae said, it's a temporary thing. Like the last server, we all played a lot for a month, and then it started to taper off. At some point, people just stop playing cause they've reached the end-game.
When that happens, I intend to simply cancel the VPS service, and maybe in a couple of months when a new FTB pack has everyone excited again, I'll start it up again.