Google Talk is built on the open XMPP specification, but when it was originally released several months back it was restricted for use with other Google Talk clients. The recently announced enhancements will make it possible for Google Talk to connect with other Jabber-based clients.
This is a major step forward, not only for Google Talk but for open standards that promote interoperability. Nice!
Also, For anyone with an interest in building IM apps that will now be able to connect with Google Talk, check out the PHP Jabber Class. It’s still a relatively young project, but I’ve found it useful for banging out prototypes of VoiceXML / IM applications. Worth a look.