Assuming you are concerned about the code you run, the location you run it in, etc. Does not provide encryption to my knowledge, but VPN can solve that.
I don't know of any truly distributed encrypted voice systems you can trust out there. Hosting your own server for a service seemed like the next rational way to solve the persons question.
Try not to think in terms of server and client being separate machines. Or thinking that a server needs to be complex or able to handle an unlimited number of nodes. It's possible to be both a client and a server. And that is in fact what Skype was doing. Some clients were also functioning as supernodes.
Assuming you are concerned about the code you run, the location you run it in, etc. Does not provide encryption to my knowledge, but VPN can solve that.
If you are looking for something more robust that can interconnect with telecom stuff, I'd suggest http://www.freeswitch.org/ or http://www.asterisk.org/