Our website provided a free download of OpenSIPS 3.0 for Mac. This free software for Mac OS X was originally created by OpenSIPS Team. The application is included in Communication Tools.
From the developer:
OpenSIPS is an open-source SIP proxy/server for voice, video, IM, presence, and any other SIP extensions. OpenSIPS is a multi-functional, multi-purpose signaling SIP server used by carriers, telecoms or ITSPs for solutions like Class4/5 Residential Platforms, Trunking / Wholesale, Enterprise / Virtual PBX Solutions, Session Border Controllers, Application Servers, Front-End Load Balancers, Call Centers, and many others.
You may want to check out more Mac applications, such as iChatMonitor, ISL Pronto or Instant Messaging, which might be related to OpenSIPS.