That be Psi, the Jabber client.
I only discovered it had an OSX port this evening. Well chuffed.
The interface will make OS X and Aqua purists vomit (it's horrible, badly designed and illogical) but as a Jabber client, it's very well-behaved and featureful.
Peter
[link|http://www.ubuntulinux.org|Ubuntu Linux]
[link|http://www.kuro5hin.org|There is no K5 Cabal]
[link|http://guildenstern.dyndns.org|Home]
Use P2P for legitimate purposes!