The most common Freeloader (v1.06B) worked on all GameCubes. It didn’t matter if it was a US, Japanese or European GameCube, the same disc worked on all. But then, the Wii was launched and the disc wouldn’t work on the US or European Wii. Datel have now fixed the problems with a updated versions for all each region. The Freeloader will only play imported GameCube games, but we all hope Datel will make a Freeloader to play imported Wii games. But we have to wait for that.
Here’s the Freeloader compatibility chart from Play-Asia: