XMeeting is a SIP and H.323 compliant and Open Source videoconferencing client for Mac OS X (10.4 and later). The current version of XMeeting is 0.3.4. Historically, XMeeting has evolved from ohphoneX. However, XMeeting has been rewritten from scratch and uses a totally different software architecture than ohphoneX.
Although not yet being a 1.xx release, XMeeting is quite stable, has good interoperability with other clients and provides many unique features such as the sophisticated Address Book integration. Much effort has been put into the Mac OS X native GUI. We think the result is worth it!