Open source means all source code is available!! Do not post any "free but not open" software here!
SIP Proxies
Mini-SIP-Proxy A very tiny perl POE based SIP proxy
MjServer cross-platform SIP proxy/registrar/redirect, written in java, based on MjSip stack
MySIPSwitch SIP Proxy server which allows using multiple SIP accounts with a single SIP login
NethidPro3.0.6 Opensource Sip Encryption Bridge: www.vonets.com
Net-SIP A Perl SIP framework that includes a stateless proxy
JAIN-SIP Proxy
OpenJSIP Opensource distributed standalone SIP proxy, SIP registrar, SIP location service run by Java VM. Based on NIST SIP and derived from JAIN-SIP Proxy.
OpenSBC: MPL licensed SIP proxy/registrar/B2BUA with NAT traversal and ENUM
OpenSER: GPL SIP Server with TLS support - renamed to Kamailio
OpenSIPS forked from OpenSER.
partysip SIP proxy server
SaRP SIP and RTP Proxy in Perl
sipd SIP Proxy
SIP Express Router (SER): the SIP router/proxy/jack-in-all-trades from IPtel.org
Siproxd SIP and RTP Proxy
SIPVicious tool suite: tools for auditing sip devices
sipX The SIP PBX for Linux: Complete, native SIP PBX solution from SIPfoundry
Vocal SIP softswitch with H.323 and MGCP translators for non-SIP endpoints
Yxa Written in the Erlang programming language
SIP Clients (UA's)
Linux clients:
Cockatoo
Ekiga || SIP, H.323 audio and video softphone for various linux, solaris, windows, and various unix systems. Formerly GnomeMeeting
FreeSWITCH: Console client for SIP, IAX2, Woomera and Jingle/Google Talk
Kphone
Linphone audio and video SIP softphone for Linux and Windows XP
minisip cross-platform SIP softphone, Linux, Windows XP and soon Windows Mobile 2003 SE
MjUA: simple cross-platform SIP softphone, written in java, based on MjSip stack
Open IP Phone Business IP Phone sdk support, ims compliant, good interoperability.
OpenSIPStack MPL licensed SIP stack with ENUM, Presence (XMPP/SIMPLE) and NAT traversal. Reference implementation of Session Border Controller (OpenSBC) available.
OpenSoftphone: A simple Java based SIP softphone using the PjSip-jni wrapper.
OpenZoep: GPL telephone and IM messaging client engine
Peers Minimalist SIP softphone written in java (tested on linux and windows)
PhoneGaim
PJSUA: Command line SIP UA with SIMPLE, IM, call transfer, RTCP/RTCP, etc.
QuteCom ex-OpenWengo: a fully SIP compliant multiplatform softphone with many features
SFLphone, open-source multiplatform multi-protocol VoIP client
Shtoom: SIP softphone in Python, runs on Windows, Mac, Linux
SIP Communicator Audio/Video phone and messenger - Multiplatform - Open Source (also supports XMPP, MSN, AIM, Yahoo! and others).
SipToSis from mhspot.com Skype SIP UA - Multiplatform - Open Source
sipXezPhone ("sipX easy phone") from SIPfoundry based on sipXtapi
sipXphone from SIPfoundry, previously known as the Pingtel phone
Twinkle
YateClient is multiprotocol and multiplatform softphone with H.323, SIP, Jingle and IAX support.
YeaPhone: A SIP softphone for the Yealink USB-P1K handset based on the libLinphone backend
MacOS X clients:
Blink: It supports wideband VoIP, Instant Messaging, File Transfer and Desktop Sharing based on MSRP
FreeSWITCH: Console client for SIP, IAX2, Woomera and Jingle/Google Talk
PJSUA: Command line SIP UA with SIMPLE, IM, call transfer, RTCP/RTCP, etc.
QuteCom ex-OpenWengo: a fully SIP compliant multiplatform softphone with many features
SFLphone, open-source multiplatform multi-protocol VoIP client
Shtoom: SIP softphone in Python, runs on Windows, Mac, Linux
SIP Communicator Audio/Video phone and messenger - Multiplatform - Open Source (also supports XMPP, MSN, AIM, Yahoo! and others).
SipToSis from http://www.mhspot.com Skype SIP UA - Multiplatform - Open Source
Telephone: A SIP softphone designed for the Mac (written in Objective-C/Cocoa). Very good integration with Mac OSX : Dial from Addressbook, dial tel: URIs from Safari, notifications with Growl.
YateClient skinnable VoIP client based on QT library which supports H.323, SIP, Jingle and IAX protocols
Windows clients
Ekiga || SIP, H.323 audio and video softphone for various linux, solaris, windows, and various unix systems. Formerly GnomeMeeting
FreeSWITCH: Console client for SIP, IAX2, Woomera and Jingle/Google Talk
JPhone Rich software SDK support softphone development, Windows, Linux, ThreadX, Vxworks etc.
Linphone audio and video SIP softphone for Linux and Windows XP
minisip cross-platform SIP softphone, Linux, Windows XP and soon Windows Mobile 2003 SE
MjUA: simple cross-platform SIP softphone, written in java, based on MjSip stack
OfficeSIP Messenger is audio-video softphone and instant messenger, open source alternative to MS Office Communicator.
OfficeSIP Softphone GPL audio-video softphone.
OpenSIPStack MPL licensed SIP stack with ENUM, Presence (XMPP/SIMPLE) and NAT traversal. Reference implementation of Session Border Controller (OpenSBC) available.
OpenZoep: GPL telephone and IM messaging client engine
Peers Minimalist SIP softphone written in java (tested on linux and windows)
PhoneGaim
PJSUA: Command line SIP UA with SIMPLE, IM, call transfer, RTCP/RTCP, etc.
OpenSoftphone: A simple Java based SIP softphone using the PjSip-jni wrapper
QuteCom ex-OpenWengo: a fully SIP compliant multiplatform softphone with many features
Shtoom: SIP softphone in Python, runs on Windows, Mac, Linux
SIP Communicator Audio/Video phone and messenger - Multiplatform - Open Source (also supports XMPP, MSN, AIM, Yahoo! and others).
SipToSis from mhspot.com Skype SIP UA - Multiplatform - Open Source
sipXezPhone ("sipX easy phone") from SIPfoundry based on sipXtapi
sipXphone from SIPfoundry, previously known as the Pingtel phone
VMukti (formerly 1videoConference) alpha: a web2.0 VoIP video conferencing software for Asterisk.
wxCommunicator Windows softphone based on sipXtapi and wxWidgets 2.8.x, multi-account, conferencing, NAT support
YateClient is multiprotocol and multiplatform softphone with H.323, SIP,Jingle and IAX support.
SIP tools
Callflow: Generates SIP Call Flow diagrams
miTester for SIP: SIP testing tool; Automates test execution.
Open Source Asterisk AMI: Open Source Asterisk AMI interface application
pjsip-perf: SIP transaction and call performance measurement tool
PROTOS Test-Suite: SIP Testing tools
SFTF: SIP Forum Test Framework - a SIP UA test suite primarily targeted at UA software developers hosted by SIPfoundry
SIP-CallerID: SIP Caller ID retrieval and lookup
SIPbomber: SIP proxy testing tool
SIP SIMPLE Command Line Tools for SIP sessions (complete console based SIP UA) and SIMPLE Presence (Publish, Subscribe, Notify) and XCAP document manipulation
Sipp: SIP performance tester
Sipper: SIPr (called Sipper) is an open source and a comprehensive SIP application testing framework. Generate any call flow in minutes.
SIP Proxy: SIP security testing tool.
Sipsak: SIP testing tool
SIP Soft client: Software development kit for SIP Softphone
SIPVicious tool suite: tools for auditing SIP devices
SMAP: Locating and fingerprinting remote SIP devices
Vovida.org load balancer: SIP Load Balancer
SIP Protocol Stacks and Libraries
Aloha Spring based J2SE SIP A/S which leverages optimistic concurrent model and supports multiple persistence models
eXosip - eXtended osip library
Juphoon SIP Stack Rich software SDK support SIP, SDP, XML, RTP/RTCP, HTTP, STUN, ABNF etc. Support Windows, Linux, ThreadX, Vxworks etc.
libdissipate SIP stack
minisip includes a SIP stack
MjSip - complete and powerful java-based SIP library for both J2SE and J2ME platforms.
MSRP Library - MSRP protocol (RFC4975) and its relay extension (RFC4976) written in Python
NIST SIP Various SIP appications and tools in Java
Open Sip Stack MPL licensed SIP stack with ENUM, Presence (XMPP/SIMPLE) and NAT traversal. Reference implementation of Session Border Controller (OpenSBC) available.
oSIP Library SIP Library
OSP client protocol stack and SIPfoundry
PhClickDial - Verona based Active/X plugin for IE allowing ClickToDial functionallity
PJSIP: Small footprint, high performance, and ultra-portable SIP stack written in C, and has language binding for Python. Works on smartphones (Symbian, Windows, iPhone/iOS, Android) as well as desktops and support ZRTP encryption.
reSIProcate SIP stack and sample Application from SIPfoundry
SailFin Adds SIP support the the Java GlassFish Application Server
sipXtackLib an RFC 3261, 3263 complient SIP stack from SIPfoundry
http://sofia-sip.sourceforge.net Sofia-Sip is SIP stack implementation with STUN and presense support
SIP SIMPLE client SDK - High level middleware on top of SIP, RTP, MSRP and XCAP protocols
Twisted Python protocol stacks and applications includes SIP support
Verona - GPL licenesed VOIP engine based on oSIP,eXosip,oRTP,ffmepg, works on Linux,Windows Mac-OS/X
Vovida SIP Vovida SIP stack
XCAP Library - XCAP client library written in Python
YASS - Statefull SIP stack used in Yate written in C++ usable for client, server or proxy in a multithread or single thread model. It's working on both Windows and Linux, it's very small but full featured.
H.323 Clients
Linux clients:
Ekiga || SIP, H.323 audio and video softphone for various linux, solaris, windows, and various unix systems. Formerly GnomeMeeting
FreeSWITCH: Console client using OPAL
GnomeMeeting
YateClient is multiprotocol and multiplatform softphone with H.323, SIP and IAX support.
MacOS X clients:
FreeSWITCH: Console client using OPAL
ohphoneX
YateClient skinnable VoIP client based on the QT library which supports H.323, SIP, Jingle and IAX protocols
Windows clients:
Ekiga || SIP, H.323 audio and video softphone for various linux, solaris, windows, and various unix systems. Formerly GnomeMeeting
FreeSWITCH: Console client using OPAL
OpenPhone
YateClient is multiprotocol and multiplatform softphone with H.323, SIP and IAX support.
H.323 Gatekeeper
GNU Gatekeeper - for Linux, Windows, Mac etc.
IAX clients
FreeSWITCH
IAXComm for Linux, MacOS X and Windows
Kiax - for Linux, Windows and MacOS, based on iaxclient, GPL
MozIAX
QtIax from http://www.holgerschurig.de/qtiax.html
SFLphone, open-source multiplatform multi-protocol VoIP client (IAX support is planned)
YakaPhoneSimple, Free, Open Source, Skinnable IAX/IAX2 Softphone from YakaSoftware
YateClient is multiprotocol and multiplatform softphone with H.323, SIP and IAX support.
RTP Proxies
AG Projects: MediaProxy 1 works with SIP express router and OpenSER, has load-balancing using DNS SRV records and accounting capabilities
Maxim Sobolev RTPproxy: Works with SIP express router to traverse NAT, also functions as RTP gateway between IPv4 and IPv6
MediaProxy 2 is more scalable using kernel space switching and works with OpenSIPs
RTP Protocol Stacks
ccRTP C++ library based on GNU Common C++
Juphoon RTP Stack Rich software SDK include RTP/RTCP stack. Support Windows, Linux, ThreadX, Vxworks etc.
JRTPLIB C++ object oriented RTP library
libRTP part of gnome-o-phone
libzrtpcpp - ZRTP extension library for ccRTP stack
LIVE.COM Streaming Media includes C++ RTP stack
oRTP Written in C, running on linux, win32 and arm-linux.
PJMEDIA: Small footprint media stack with a tiny RTP/RTCP stack suitable for DSP or embedded deployment
RTPlib C library
sipXmediaLib RTP + audio bridges, audio splitters, echo suppression, tone from generation (e.g. DTMF), streaming support, RTCP, G711 codecs, etc. from SIPfoundry
Secure RTP - see: SRTP
UCL Common Multimedia Library includes cross platform RTP stack
Vovida RTP Stack
YRTP - Yate RTP stack, that can be used in other projects.
zrtp4j - ZRTP stack for Java, based on GNU ZRTP, used in SIP Communicator
MSRP Relays
MSRPRelay from AG Projects
XCAP servers
OpenXCAP from AG Projects
Other tools
Encours Teleconferencing in your web browser with an integrated VOIP layer (Java) and an optional Asterisk connectivity on the server side.
Howler Technologies - optimised G.729 codec for softswitch market.
MORCC - automated online Calling Card store. Paypal integrated.
OgonPhonesXML .NET Library for Aastra SIP Phones and Cisco SIP/IP phones for fast and easy XML Interfacement.
Oreka capture and retrieval of SIP, Cisco Skinny (SCCP) and raw RTP sessions with audio compression, rdbms metadata storage and web based user interface.
Vovida.org STUN server: A STUN server
Voipong - Voice over IP (VoIP) sniffer and call detector.
Vomit converts a Cisco IP phone conversation (recorded with TCPdump) into a standard WAV file
PBX platforms
Some of these include SIP proxy functionality
Asterisk: Open Source PBX. Supports IAX, SIP, MGCP, H.323 and other protocols
CallWeaver: a fork of Asterisk with T.38 termination
FreeSWITCH Open Source PBX and Soft Switch
OpenPBX: Open Source PBX developed using Perl
PBX4Linux: ISDN PBX with H.323 GW
SIPexchange PBX Pingtel's SIP PBX
sipwitch: GNU project's Pure SIP call server, sipwitch on freshmeat.net
sipX - The SIP PBX for Linux from SIPfoundry, sipX on freshmeat.net
SIP - It's the Rage! - Rage! Business Office Xchange based on SipFoundry
YATE Yet Another Telephony Engine - supports H.323, SIP, IAX, PSTN
IVR platforms
Asterisk: Open Source PBX with built-in IVR server
Bayonne: GNU project IVR server
CT Server Perl based Open Source client/server library supporting Voicetronix Telephony hardware.
FreeSWITCH
OpenVXI: Implementation of VoiceXML
SEMS: Free/Open Source SIP media server with IVR capabilities
sipX PBX The SIP PBX for Linux (open source) with built-in IVR (voice mail & auto-attendant)
YATE Yet Another Telephony Engine
See Also: VoiceXML
Voicemail servers
Asterisk: Open Source PBX with built-in Voicemail Server
FreeSWITCH
Lintad: Linux Telephone Answering Device - A Voice and Faxmail Server
OpenPBX: Open Source PBX with built in voicemail
OpenUMS: Linux Voicemail and Unified Messaging Server
SEMS: Free/Open Source SIP media server with built-in Voicemail and Voicebox Server
sipX PBX The SIP PBX for Linux (open source) with built-in IVR (voice mail & auto-attendant)
VOCP: A Voicemail Server for voice modems
YATE Yet Another Telephony Engine with H.323, SIP and IAX support.
Speech
Text-to-speech and speech-to-text (voice recognition)
Festival: Voice synthesis system (implemented with a trainable neural network)
OpenSALT: Implementation of SALT
OpenVXI: Implementation of VoiceXML
Sphinx: speaker-independent speech recognizer
UniMRCP: cross-platform MRCP client and server
Fax Servers
Asterisk Fax Email Gateway
Lintad: Linux Telephone Answering Device - A Voice and Faxmail Server
Hylafax
Development platforms, protocol stacks
H323plus: Open Source H.323 Protocol Stack following on from the original openH323
OpenBloX: OpenBloX Open Source Java Diameter framework with all IMS and SIP servers interfaces; maintained by Traffix Systems,
OpenMGCP: Open Source MGCP Protocol Stack Developed with C and POSIX APIs,
OpenSS7: SS7 Protocol Stack
ooh323c: Open Source H.323 Protocol Stack Developed in C
++Skype C++ library for skype add-on platform independent software development. It is platform independent, easy to use, and easy to extend because of the flexible library design, inspired by modern C++ design ideas. Performance is one of the goals.
Radius Servers
Aradial: Radius server and Billing for VoIP
BSDRadius: Radius server for VoIP
Interlink RADIUS Server RADIUS Server Software
RadBox RADIUS Server + Billing System. (For a work, you nead instal Framework 2.0)
Billing
See Open Source Billing Systems
Codecs
See Codec Software
Middleware
Ernie: Open Source Python based applications platform for VoIP and presence based applications
Mobicents: The most popular Open Source Service Logic Execution Environment (JSLEE) and SIP Application Server for the Java platform.
TALK: Web based CTI Solution (AJAX client) which provides call control, presence and directorty features.
Suite Solutions
Zoontelecom: Zoon Suite is a Open Source solution for make VoIP services with billing and more. (Spanish)
CTI Dialer utilities
Asterisk phonebook A common shared phone book directory for Asterisk PBX
TALK Powerful directory management and scalable architecture to create Click to call or Select and Dial applications + AJAX libraries to implement these features in your web site.