Open source software runs a large share of the world’s voice infrastructure. This page is a working list of the projects we consider active and worth evaluating, grouped by what they actually do. Every link here was checked in August 2026, and anything that had gone dead, been abandoned, or lost its domain has been removed rather than left to rot.
Some of the projects below are ours, and the rest of what we publish is on the ICT Innovations open source projects page. If a project you rely on is missing, or you spot something here that has since gone quiet, open a ticket and we will review it.
Softswitches and telephony engines
FreeSWITCH
A cross-platform, scalable, multi-protocol softswitch. It handles high call volumes well and is widely used as the media server in carrier and enterprise deployments. Now maintained under SignalWire. FreeSWITCH is the engine behind ICTFax, ICTPBX and ICTCore.
github.com/signalwire/freeswitch
Asterisk
The open source telephony framework that made software PBXs mainstream. Asterisk is not a finished PBX product on its own, it is a toolkit you build on, which is why most deployments sit behind a management layer. It is the engine behind ICTContact and ICTBroadcast.
asterisk.org · github.com/asterisk/asterisk
Kamailio
A high-throughput SIP proxy, registrar and call router. Commonly placed in front of a media server to handle signalling, routing and security at scale.
kamailio.org · github.com/kamailio/kamailio
OpenSIPS
A SIP proxy, router, registrar and redirect server aimed at service providers running SIP telephony for their own customers. Overlaps heavily with Kamailio, and the choice usually comes down to which routing model and module set fits your build.
opensips.org · github.com/OpenSIPS/opensips
GNU Gatekeeper
An H.323 gatekeeper built on the OpenH323 stack, providing address translation, admission control, call routing and accounting. Still maintained, and relevant if you have H.323 endpoints or video gear that predates a SIP-only network.
gnugk.org
PBX platforms and management interfaces
FreePBX
A web interface for Asterisk, maintained by Sangoma. It does one job well, which is making a single Asterisk PBX configurable without deep Asterisk knowledge. Multi-tenant and white label use needs significant customisation.
freepbx.org
FusionPBX
A multi-tenant PBX management platform built on FreeSWITCH, aimed at service providers who need domain-based tenant separation, carrier switching and call center features from one install.
fusionpbx.com · github.com/fusionpbx/fusionpbx
ICTPBX Community Edition
Our own free, open source multi-tenant IP PBX, built on ICTCore and FreeSWITCH with an Angular front end. Released under MPL 2.0. Aimed at ISPs and ITSPs who want tenant isolation and white labelling without per-seat licensing.
github.com/ictinnovations/ictpbx-community-edition · ictpbx.com
Call center and dialer platforms
GoAutodial
A web-based inbound and outbound call center suite built on Asterisk, derived from the VICIdial lineage. Long-running project with an established installed base.
goautodial.org
OSDial
A predictive dialer built on Asterisk, also descended from the VICIdial codebase, packaged as a self-contained install.
osdial.com
ICTDialer
Our open source unified communications autodialer, with voice, SMS and fax broadcasting, built on the FreeSWITCH-based ICTCore framework. Note that the hosted service at ictdialer.com is a separate Asterisk-based product that shares the name.
github.com/ictinnovations/ictdialer
Communications frameworks
ICTCore
An open source unified communications framework for developers and integrators. It lets you build communication applications such as auto attendant, fax to email and click to call, with custom business logic controlling inbound and outbound calls, using PHP rather than dialplan scripting.
ictcore.org · github.com/ictinnovations/ictcore · docs
Fax over IP
ICTFax
An open source fax server covering email to fax, fax to email, web and REST API sending, with T.38 and G.711 support. Multi-tenant, built on FreeSWITCH and ICTCore.
ictfax.org · github.com/ictinnovations/ictfax · docs
AI and automation for telephony
asterisk-ai-voice-agent
An open source AI voice agent for Asterisk, derived from the ICTContact engine. Handles the audio path and turn-taking so you can put a language model on a live call.
github.com/ictinnovations/asterisk-ai-voice-agent
pbx-mcp
A Model Context Protocol server that exposes Asterisk AMI and FreeSWITCH ESL to AI assistants, so a model can query channels, endpoints and call state through a defined tool interface instead of raw socket access.
github.com/ictinnovations/pbx-mcp · docs
SIP stacks and developer libraries
PJSIP
A high-performance SIP and media library written in C, with multimedia support, used in both embedded and desktop VoIP applications. The stack behind a large number of mobile softphones.
pjsip.org
JsSIP
A JavaScript SIP library that turns any web page into a SIP endpoint over WebSocket, with audio, video, messaging and presence. Works with Kamailio, OpenSIPS and Asterisk.
github.com/versatica/JsSIP
SIP.js
A full SIP stack in JavaScript, built for putting WebRTC audio, video and data into an application. Actively maintained, and the usual alternative to JsSIP.
github.com/onsip/SIP.js
asterisk-ami-node and freeswitch-esl-node
Our Node.js clients for the Asterisk Manager Interface and the FreeSWITCH Event Socket Layer, for scripting call control and event handling in JavaScript.
asterisk-ami-node · freeswitch-esl-node
Billing and rating
ASTPP
An open source VoIP billing platform built on FreeSWITCH, covering Class 4 and Class 5 switching, rating, invoicing and reseller management.
astppbilling.org · github.com/inextrix/ASTPP
A2Billing
A real-time billing engine and calling card platform for Asterisk, covering prepaid and postpaid rating, DID management and callback services.
asterisk2billing.org
P-KISS-SBC
The successor to pyfreebilling, a session border controller and wholesale billing platform for FreeSWITCH aimed at carrier and wholesale traffic. The old pyfreebilling.com address now redirects here.
pk-sbc.io
CitrusDB
A multi-user billing package for internet, subscription and telecom services, with CRM, ticketing and invoicing. Long-established, though development moves slowly, so check recent activity before committing to it.
citrusdb.org
Softphones and clients
Linphone
An open source SIP softphone for desktop and mobile with voice, video and instant messaging, usable with any SIP provider. One of the better maintained clients in this category.
linphone.org
Jitsi
A set of open source projects for secure video conferencing, built around Jitsi Videobridge and Jitsi Meet, with dial-in, recording and simulcast available through related components.
jitsi.org
Sipdroid
A SIP and VoIP client for Android, still receiving updates.
sipdroid.org · github.com/i-p-tel/sipdroid
Lumicall
An Android app for encrypted SIP calling, built to interoperate with standard SIP servers and corporate phone systems.
lumicall.org · github.com/opentelecoms-org/lumicall
Projects removed from this list
These appeared in earlier versions of this page and are no longer recommended. We are listing them so anyone who found this page through an old link knows why they are gone.
- RasPBX, the Asterisk and FreePBX image for Raspberry Pi. Its domain no longer belongs to the project and now redirects to an unrelated gambling site. Do not visit the old address.
- Freeside, billing and provisioning software. The project site no longer resolves.
- sipML5, the HTML5 SIP client. Archived on GitHub since 2020. Use JsSIP or SIP.js instead.
- CSipSimple, the Android PJSIP client. Development stopped in 2016 and the Google Code project is a read-only archive.
- Siphon, the iPhone PJSIP client. Hosted on Google Code, which shut down in 2016.
- Ekiga, the softphone and video conferencing client. No release since 2013.
- WEBRTC-to-SIP, a WebRTC to Kamailio bridge demo. No commits since 2023, and the same job is better handled by JsSIP or SIP.js against a current Kamailio build.
Last reviewed September 2026. Every link above returned a live response and every project was checked for recent development activity at that time.
What we publish ourselves
Fax is the part of this list we know best, because we have been shipping a fax server since 2009. Everything here is on GitHub and installs without talking to us first.
- ictfax is the fax server itself. T.38 and G.711, a web interface for users and tenants, and Docker images on both Docker Hub and GHCR so you can try it without building anything.
- ictcore is the framework underneath it. One REST API covering voice, fax, SMS and email, which is why the fax server and the PBX share so much code.
- ictfax-mcp connects an AI assistant to a running ICTFax install. It reads the fax queue and delivery status; sending stays behind a flag you have to set yourself.
- langchain-ictfax is the same capability as a LangChain toolkit, on PyPI, for agents built with LangChain rather than an MCP client.
- ictpbx-community-edition bundles the PBX and the fax server behind one interface, free under MPL-2.0, with an Ansible role if you would rather not install by hand.
Here is a short walkthrough of the fax server, from a Docker pull to a sent fax. The full list of what we maintain, including the developer libraries, is on the projects page.