Lameboy is the ultimate Gameboy and Gameboy Color emulator for the Nintendo DS.
How To Set Up Lameboy on the R4
1. Download Lameboy here.
2. Make a folder in the root of your memory card entitled "lameboy".
3. Put there all the contents of lameboy as well as your gb and gbc roms.
To try it now, download Pokemon Yellow Version here.