Unified Communications System - PBX System
Java VoIP Softphone (SIP) (replaced by jfPhone)
High performance, production quality STUN server and client library
H.323 Gatekeeper for VoIP and videconferencing
Baresip is a modular SIP User-Agent with audio and video support
Optimized and cross platform SMPTE 2022 FEC library in C, Python, Java
Respins of various open source PBX projects
C++ SIP stack based on Chrome source code