SIP Communicator started out at the Louis Pasteur University in Strasbourg, France (http://www-ulp.u-strasbg.fr) but has grown to include members and contributors from (alphabetically) Brazil, Bulgaria, Germany, Japan, Spain, UK, USA, and others.
SIP Communicator is an audio/video Internet phone and instant messenger written in Java. It supports some of the most popular instant messaging and telephony protocols such as SIP, Jabber (and hence GoogleTalk), AIM/ICQ, MSN, Yahoo! Messenger and soon others like IRC, and IAX. SIP Communicator is completely Open Source / Free Software, and is freely available under the terms of the GNU Lesser General Public License.
SIP Communicator is based on the OSGi (http://osgi.org) architecture using the Felix implementation from Apache. This makes it very extensible and particularly developer friendly.