You can also make a reply here: http://www.xfire.com/xf/modules.php?name=Forums&file=viewtopic&p=404309#404309
In the meantime, if you simply want to use in-game chat (as a temporary, until it's hopefully officially supported), you can add this to the end of xfire_games.ini -
[9999]
LongName=Galactic Civilizations 2
ShortName=galciv2
LauncherDirKey=HKEY_LOCAL_MACHINE\SOFTWARE\Stardock\Drengin.net\GalCiv2\Path
LauncherEXE=GalCiv2.exe
Launch=%UA_LAUNCHER_EXE_PATH% %UA_LAUNCHER_EXTRA_ARGS%
InGameRenderer=D3D9
(Note that any custom additions to xfire_games.ini are removed whenever the file is updated)