On what? The original poster, who isn't a programmer, porting source code that isn't available? One of the suggestions put forth to port other closed-source applications? BlackBerry OS is a proprietary, closed source operating system. That prevents anyone but RIM from making an actual port. Someone with a great amount of time and skill might be able to craft sufficient device drivers and other hacks to get Blackberry OS running on an N900, but the license for the OS likely forbids that.