Java VoIP Softphone (SIP) (replaced by jfPhone)
Accent interfaces and controls systems through goals and policies
Java VoIP/SIP PBX system (replaced by jfPBX)
Optimized and cross platform SMPTE 2022 FEC library in C, Python, Java
The OZEKI VoIP Service Checker allows you to check VoIP services.
C++ SIP stack based on Chrome source code