Wow, how did I never know about this thing? For those that don't know, Freeloader allows ANY Gamecube to play ANY Gamecube game from anywhere. So, if you have a UK Gamecube you can use Freeloader to play U.S. versions of games; it's a swap disc (put the Freeloader disc in then when prompted, swap it out and put in whatever game you want). If you have a U.S. Gamecube, you can play any UK or Japanese game, etc. Read about it here and there is a review of it here.
Now, will this work on Wii, I'm not sure, but it should work. When ever you put in a Gamecube game into Wii and start up the game, the Wii basically becomes a Gamecube, so it should work unless Nintendo has intentionally made it so Freeloader won't work. Hope it does work.