Ben_Larson, on Sat Apr 3, 2010 6:19 PM, said:
You need to get devkitPro - it's a free toolchain for development on Gamecube (among other systems) that you can download. I think there's a Gamecube graphics library included that has some demos that should get you started. This is all C development, BTW. I used devkitPro to port a game to the Gamecube a while back.
Actually testing on the console itself is kind of a pain in the ass, though - you'll need a Gamecube memory card to SD converter for one, and a USB to SD card converter as well in order to copy your game onto the SD card from the computer. There's sites online that should explain all the software you need and the procedure for getting things up and running. Feel free to PM me if you need more help.
Or you can hunt down a Dolphin Gamecube Development Console and get all the needed wires and software for it, as well. However, that's much more difficult.
Most programming for it is done in C/C++.
I should warn you, I've heard bad things about Gamecube development. I hear it's literally one of the most difficult consoles to get games working well on.