It's frankly not really a matter of "figuring it out". If the company behind eBuddy decides to release a version for the N900, then they'll probably have a press release; if they don't we can't really do anything about it. That said, the N900 already has a pretty good integrated IM/VoIP system which is also extensible. Some of the plugins (Pecan/Butterfly, I'm looking at you...) are still a bit buggy, but that can be improved. To reiterate my earlier post,and nosa101's, is there something that the current chat framework or plugins lack? In my opinion, it would be better to make the (already good) chat framework in Maemo be even more awesome than to try to convince a company to make a third-party app to replace it (even if they'd listen).
So tell us, what is the current system lacking? What do you like about eBuddy that it doesn't do, or does differently? Heck, write it up and put it in the maemo.org Brainstorm.