Every game playable on the DS gets extra points in my book! A solid 11/10.
They're playing the GBA version of the game, likely using GBARunner2.
On DSi you can do this with software mods, or using a flashcart (R4i, etc.)
On DS / DS Lite, softmod isn't an option, but you can also use a GBA flashcart such as the EZFlash Omega or EverDrive GBA X5.