It's not unique, it's just XMPP + Mumble.
I used to play with a large community and every time a new game would come out we'd always setup forum software, an XMPP (chat software) server and a Mumble server for that game. This was pretty easy to get done because we were all working in tech, but if you were an average gamer it wasn't something that you could handle.
Discord packaged the text, voice and forum software into one application and they handle the server hosting. It only costs all of your privacy and $10/mo.