No they didn't buy the rights to gameboy emulation, they
patented it on handhelds. It's an invalid patent if anyone challenges it though, the patent was made last year (or was it this year? I forget), and there is previous art going back to 1998 at the very least.
I remembered another one that's supposed to be good, though I haven't tried it myself, GnuBoyCE.
Take a look here for about every GameBoy emulator:
http://www.pocketgamer.org/games/emu...tml#Game%20Boy
Most come up 404, but at least you have names to search for (or you could try looking up the URL on
www.waybackmachine.org ). Most of them are gone not because of Nintendo, but by the amount of time that has passed.