SIP Applications (Proxy, PBX, ...)

    * Sip Express Router (ser): Highspeed GNU SIP proxy with a lot of features and a lot of 
ongoing development. Homepage: http://www.iptel.org/ser/. (there is also a new homepage 
comming). A really cool SIP proxy - I like it! You can also take a look at the development 
homepage with web CVS. At the beginning you should read the admin guide and the mailing 
lists archive.
    * Openser: A fork of the Sip Express Router, more development and more new features 
compared to ser. Homepage: http://openser.org/.
    * Ser Media Server (sems): Media Server add-on for ser SIP proxy. Homepage: 
http://developer.berlios.de/projects/sems. Supports voicemail, IVR, SIP/PSTN gateway 
(supported cards) ...
    * Asterisk: Linux Software PBX with Gateway, SIP Proxy, Gateway (SIP, H.323, PSTN, 
...); Homepage: http://www.asterisk.org/
    * OpenPBX: A fork of Asterisk; Includes channels and applications which are not in 
stock Asterisk release due to missing disclaimer; Homepage: http://www.openpbx.org/
    * partysip: A Linux SIP proxy based on osip2 (LGPL). Developer homepage is at: 
http://savannah.nongnu.org/projects/partysip/, you can download tar packages from: 
http://www.antisip.com/download/.
    * Bayonne: A Linux Telephony server which supports SIP and H.323. Includes a SIP 
proxy/registrar. Homepage: http://wiki.gnutelephony.org/index.php/GNU_Bayonne.

    * SIP TAPI: A TAPI driver for MS Windows. Allows to make SIP calls from Outlook or any 
other TAPI application. Based on AstTapi and eXosip2. GPL. Homepage: 
http://www.enum.at/index.php?id=479.
    * mysip: A SIP proxy server from Siemens for Windows platforms. Homepage: 
http://www.mysip.ch/
    * Fomine RTC server: A SIP proxy server for Windows which uses its own SIP stack (does 
NOT need the RTC API) Homepage: http://www.fomine.com/rtc-server.html. The unregistered 
version can be used up to 5 users.
    * sipXpbx: Part of pingtel's open source releases for VoIP. License: LGPL; Homepage: 
sipfoundry.org. This PBX combines various sipX applications like a SIP proxy (sipXregistry, 
sipXproxy), a media server (sipXvxml) and lots more.
    * yate: Yet Another Telephony Engine - a PSTN gateway. License: GPL; Homepage: 
yate.null.ro. This gateway supports H.323, SIP and zaptel (->asterisk) based PSTN cards.
    * yxa: YXA is a SIP proxy written in Erlang. License: BSD; Homepage: 
http://www.stacken.kth.se/projekt/yxa/index.html.
    * Freeswitch: Freeswitch is a multi protocol (SIP, IAX, jingle ...) softswitch written 
in C. Runs on Linux, BSD, Windows ... Homepage:http://www.freeswitch.org/.