I don't really get that part. You have everything needed to build it yourself (and so host it) on the wiki [0].
Also, everytime someone builds something now, it seems to be the first comment out there "it needs to be self-hosted". I get that this is a security oriented communication app, so it needs to be audited and open sourced so we can trust it, but now that this part is OK, people are finding something more to ask: the self-hosting part.
I would say that it is a valid question, because the answer sheds some light on the architecture and goals (or business model) of a project. It also reflects a (healthy) renewed interest in reducing our dependency on cloud services; because of privacy concerns or legal implications for example.
It is also not immediately apparent from Ring's website and wiki. The developers of Ring are quite helpful in replying here on HN though.
Ring.cx run server-less. It use the same technologies as Bittorrent (DHT tables) to find and connect users. You can also self host a server such as Asterisk or Freeswitch in a VM if you like, this is supported too, so is inter-operability with commercial VoIP providers.
