VOIP PBX and Servers

• Asterisk: Open Source PBX
• Bayonne: Open source PBX
• FreeSwitch: Open source cross platform (*nix, Win, OSX) multiprotocol (SIP, IAX, Googletalk, Jabber, XMPP, WOOMERA/H.323, PRI/T1/E1) softswitch.
• CallWeaver: Vendor independent, cross-platform open source IP-PBX, originally derived from Asterisk.
• OpenSER: Flexible and powerful open source GPL SIP ( RFC3261 ) server with integrated TLS
• Sip Express Router: High-performance, configurable, free SIP ( RFC3261 ) server
• sipX Solution Summary: SIPfoundry - The SIP PBX for Linux (L-GPL)
• YATE - Open Source Linux/Windows GPL Telephony Server and Client (has support for SIP, H.323, IAX2, E1/T1, voicemail), H.323 - SIP translator.
• more...