opensips is described as 'OpenSIPS (Open SIP Server) is a mature Open Source implementation of a SIP server. OpenSIPS is more than a SIP proxy/router as it includes application-level functionalities. OpenSIPS, as a SIP server, is the core component of any SIP-based VoIP solution' and is an app in the Social & Communications category. There are more than 10 alternatives to opensips for a variety of platforms, including Linux, Mac, Windows, Android and iPhone. The best alternative is Asterisk, which is both free and Open Source. Other great apps like opensips are 3CX Phone System (Freemium), FreePBX (Free, Open Source), Wazo (Free, Open Source) and FreeSWITCH (Free, Open Source).
FreePBX is a web-based open source GUI (graphical user interface) that controls and manages Asterisk (PBX), an open source communication server. FreePBX is licensed under the GNU General Public License (GPL), an open source license.
FreeSWITCH is a scalable open source cross-platform telephony platform designed to route and interconnect popular communication protocols using audio, video, text or any other form of media. It was created in 2006 to fill the void left by proprietary commercial solutions.
More than a PBX, with Elastix you can communicate with your customers through voice, video and live chat from anywhere. Built-in video conferencing, website live chat and smartphone apps, ensure your agents remain productive through one unified mobile solution.
uSipSwitch a micro sip switch (sip proxy) perfect for edge SIP SBC work (e.g. hosted PBX business). Comes with web console and DNS health tools. Uses modern clustering NoSQL technology for advanced HA.
sipXcom provides complete enterprise-grade telephony, unified messaging, Instant messaging, audio conferencing, and many other features. sipXcom can be run along side your existing Cisco, Avaya, Mitel, Shortel or other PBX while you migrate users to the sipXcom system.