So that makes it akin to the XBox, in that you have to FTP from the box to the PC? Or a poorer version of that? Do you have a link to how to do that with a Game Cube?
Xbox games can be backed up, but of course you need to alter the system to play them. Similar to the PS2.
Gamecube games need to be backed up similar to how Dreamcast games were, you need to log into it and pull the data to your computer. I forget the cables needed though. Even after that is done, you need to alter your Gamecube to play them (modded). And to top it off, I think there is currently only a mod that uses the swap trick (put original in, swap with backup). Unfortunately, they did such a good job with this system's protection that by the time a convienent way to backup your games is discovered, they'll be into their next generation console.