Gabber 2 is the next generation of Gabber: The Gnome Jabber Client. Gabber 2 is a Jabber client written in C++ using Gtkmm2 which is currently available for Linux and Mac OS X (under X11).
Experimental versions are available for Windows.
Temas and Julian, the main project leads for Gabber, are looking for someone else to lead up Gabber development.
The first thing a new project lead would have to do is get Gabber 2 working with gtkmm 2.4. This will take some major architectural changes to Gabber.
Lots of users seem more than happy with Gossip and Gaim, so if no one steps up to the plate for project lead, Gabber development will in all likelihood cease.
I know that I would be more than happy to continue development of Gabber as a secondary developer and provide user interface design. So, if you're interested, start looking at the code and see what can be done to get it working nicely with gtkmm 2.4 (hint: it can't crash or have memory leaks when windows close--even when the window wants to close itself)
Be sure to check out the forums for casual discussion along with the official feature request and bug lists to help steer the future direction of Gabber 2.