- [Asterisk](http://www.asterisk.org/) - Easy to use but advanced IP PBX system, VoIP gateway and conference server. `GPL-2.0``C`
- [ASTPP](https://www.astppbilling.org/) - is an Open Source VoIP Billing Solution for Freeswitch. It supports prepaid and postpaid billing with call rating and credit control. It also provides many other features. ([Source Code](https://github.com/iNextrix/ASTPP)) `AGPL-3.0``PHP`
- [Freepbx](http://www.freepbx.org) - Web-based open source GUI that controls and manages Asterisk. ([Source Code](http://git.freepbx.org/projects/FREEPBX)) `GPL-2.0``PHP`
- [FusionPBX](https://www.fusionpbx.com/) - Open source project that provides a customizable and flexible web interface to the very powerful and highly scalable multi-platform voice switch called FreeSWITCH. ([Source Code](https://github.com/fusionpbx/fusionpbx)) `MPL-1.1``PHP`
- [Homer](https://www.sipcapture.org/) - Troubleshooting and monitoring VoIP calls. ([Source Code](https://github.com/sipcapture/homer)) `AGPL-3.0``Angular/C`
- [Kamailio](http://www.kamailio.org/w/) - Modular SIP server (registrar/proxy/router/etc). ([Source Code](https://github.com/kamailio/kamailio)) `GPL-2.0``C`
- [Kazoo](http://2600hz.org/) - KAZOO is an open-source, highly scalable software platform designed to provide carrier-grade VoIP switch functions and features. ([Source Code](https://github.com/2600hz/KAZOO)) `MPL-1.1``Erlang`
- [Freepbx](http://www.freepbx.org) - Web-based open source GUI that controls and manages Asterisk. ([Source Code](http://git.freepbx.org/projects/FREEPBX)) `GPL-2.0``PHP`
- [FusionPBX](https://www.fusionpbx.com/) - Open source project that provides a customizable and flexible web interface to the very powerful and highly scalable multi-platform voice switch called FreeSWITCH. ([Source Code](https://github.com/fusionpbx/fusionpbx)) `MPL-1.1``PHP`
- [Kazoo](http://2600hz.org/) - KAZOO is an open-source, highly scalable software platform designed to provide carrier-grade VoIP switch functions and features. ([Source Code](https://github.com/2600hz/KAZOO)) `MPL-1.1``Erlang`
- [Wazo](http://wazo.community/) - Full-featured IPBX solution built atop Asterisk with integrated Web administration interface and REST-ful API. ([Source Code](https://github.com/wazo-pbx)) `GPL-3.0``Python/PHP`