We have Orbiter running under Windows CE 4.2, Windows XP/98 and linux (debian), so it's not very difficult to implement one to run on a Nokia 770. All you have to do is find a graphic engine which works under Internet Tablet 2005 and derive from Orbiter to implemented the methods to render pictures, draw lines, etc. We are using SDL and Pocket Frog graphics engines. If you're lucky, SDL might work under IT2005 and all you'll need to do is recompile it with "maemo development platform" from nokia.
Best regards,
Chris M.