I just gave it a shot with freedroids-classic. It compiles without any mofifications in the SDK and I can run it on the x86 target. I have no idea how the input is supposed in this Xephyr nested X server, I seem to be able to shoot when i tap the mouse but can't move yet. Also playing ogg files (the theme i think), does not work as i compiled withou libvorbis for testing - which does not matter as there is no sound device available in my SDK anyway. Now compiling it in the ARMEL target and then will copy it over to my n900 to giv it a shot. If that works I'd package it - should make a nice littleproject the get known to debian packages I would expect that FreedroidsRPG, which this thread is about also can be compiled for n900 withou major changes.
Will post here when freedroids classic runs on the n900.