You may want to contact LinuxHacker from the above links that epage suggested, as Homeworld is already almost ported to Pandora -- nearly the same hardware as N900.
http://pandorawiki.org/Projects_Under_Development#Games

It is interesting that in the near future we might see a lot of good code exchange between N900 and Pandora, which is a special gaming platform with developer interest. Similarly DIY electronics crowds are developing on Beagle Board, which may result in nice codec optimizations etc on all these similar platforms. Linux FTW!