Yeah, i know why he has the time / energy... He wrote it's his main job, he earns enough money with his NO$GBA debugger.....
i don't want to write a gba emulator, but a nds emu ^^
there is an emu for each nintendo system which does its job very great: virtual gameboy, Project64/1964, zsnes ...... but there are not many very good emus for the newer systems like ngc and nds. i think it's a bit harder today, the newer systems are harder to emulate. additionaly the progress of developement of pc cpus has slowed down...