It definitely existed earlier than that. I found an old project in my backups for a 3d space game that dates from 2003 and can see a CVS update history on the web archive that stretches back to 2002.
Not sure what the launch in 2005 entailed, probably a rebranding and freshening up to make it seem more serious and appealing to developers, but it was already one of the better 3d frameworks around at the time. I was able to extend it to support LUA scripting in my game engine, was well abstracted and really nice to work with.
