SIP Communicator Open Source VoIP & IM | SIP Communicator is an audio/video Internet phone and instant messenger that support some of the most popular instant messaging and telephony protocols such as SIP, Jabber, AIM/ICQ, MSN and soon others like Yahoo and IRC. SIP Communicator is completely Open Source / Free Software, and is freely available under the terms of the GNU Lesser General Public License.
RESOURCES: The SIP Communicator FAQ can usually answer most questions. You can also ask on the users mailing list, or at the irc channel #sip-communicator at irc.freenode.net.
Note: Right now SIP Communicator is still a work in progress and as such is still unstable. If you would like to help or follow project progress check the Project Roadmap or join our Mailing Lists. You can also have a look at the SIP Communicator screenshots Thanks for your patience and continuing support! The SIP Communicator team