Raid Call

Raidcall is an audio service based on Cloud-computing. Both the client and server software are free for all normal users (non-commercial). You can save money on server rental fee, and save time from sophisticated configurations.

raidcall.com

I'm currently asking them if it's as well an open source although it says "non-commercial", as well I don't see a license anywhere on their homepage or links on the bottom of page.