freepbx!

3CXPhone is a free VoIP phone available for Windows, iPhone or any Android based smart phone such as Google Nexus, Sony Xperia, Motorola Droid or Samsung Galaxy. Connect 3CXPhone to a VoIP provider or to a VoIP PBX (for example 3CX Phone System) to make calls to any VoIP, mobile or landline number.

FusionPBX is an open source FreeSWITCH GUI. FusionPBX can be used as a high available single or domain based multi-tenant PBX, carrier grade switch, call center server, fax server, voip server, voicemail server, conference server, voice application server, appliance framework and more. FreeSWITCHtm is a highly scalable, multi-threaded, multi-platform communication platform. FusionPBX license is the MPL 1.1 license.

Starfish PBX aims to be an open source alternative to Digium’s Switchvox. The goal is to have a software equivalent to which we can add additional functionality like:

The MiRTA PBX is an interface written in PHP using Mysql as backend to manage a multitenant PBX built over the Asterisk Open Source PBX. An easy to use interface allows you to manage one or more Asterisk PBX in a multi tenant, load sharing and high availability configuration. All configurations are stored in a database to be easily integrated into existing CRM or billing software. All features usually embedded in a professional PBX can be found in Asterisk and in MiRTA PBX interface.

Thirdlane Business PBX platform provides all of the easy-to-use advanced communications features businesses need, with the flexibility for customization and growth - at a fraction of the cost of competitive solutions.

Ombutel is a joint venture of Telesoft and Xorcom that offers a free phone system based on the solid Linux and Asterisk platforms, offering whole new level of user experience with offers fully-responsive user interface that looks great, and is easy to use, on any screen size. Ombutel utilizes the latest technologies in Linux and Asterisk to provide a highly secure system on all levels.

Yate is a softswitch (concept of separating the network hardware from network software).

Elastix is an open source Unified Communications Server software that brings together IP PBX, email, IM, faxing and collaboration functionality. It has a web interface and includes capabilities such as a Call Center software with predictive dialing.

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. With a very flexible and customizable routing engine, OpenSIPS unifies voice, video, IM and presence services in a highly efficient way, thanks to its scalable (modular) design.What OpenSIPS has to offer, comes in a reliable and high-performance flavour - OpenSIPS is one of the fastest SIP servers, with a throughput that confirms it as a solution up to enterprise or carrier-grade class. »

Kamailio® (successor of former OpenSER and SER) is an Open Source SIP Server released under GPL, able to handle thousands of call setups per second. Among features: asynchronous TCP, UDP and SCTP, secure communication via TLS for VoIP (voice, video); WebSocket support for WebRTC; IPv4 and IPv6; SIMPLE instant messaging and presence with embedded XCAP server and MSRP relay; asynchronous operations; IMS extensions; ENUM; DID and least cost routing; load balancing; routing fail-over; accounting, authentication and authorization; support for many backend systems such as MySQL, Postgres, Oracle, Radius, LDAP, Redis, Cassandra, MongoDB, Memcached; XMLRPC control interface, SNMP monitoring. It can be used to build large VoIP servicing platforms or to scale up SIP-to-PSTN gateways, PBX systems or media servers like Asterisk™, FreeSWITCH™ or SEMS. Kamailio and the SIP Express Router (SER) teamed up for the integration of the two applications and new development. »