Issabel PBX - Unified Communications
ICTCore: Unified Communications Framework for web developers
High performance, production quality STUN server and client library
Accent interfaces and controls systems through goals and policies
H.323 Gatekeeper for VoIP and videconferencing
SIP Video Multiconference Media Server with WebRTC support.
Java VoIP/SIP PBX system (replaced by jfPBX)
Web interface for OpenSIPS
C++ SIP stack based on Chrome source code