Language is German only.

According to this website, it's not:

Please provide some proof

Oops, forgot I made this thread.

Anyway, I'd say the burden of proof would be on whoever added the ogdb entry. They probably copied it from the PS2 version which does indeed contain all 5 languages. Note how the site claims that this also includes the voices which would be impossible to fit in the disc space on the GameCube. Also, the UK and French releases for GameCube contain only their respective languages as you can see on redump.

There was no language select I could find in-game and the game would only boot up in German regardless of my IPL language. Unless there's an option buried somewhere that I missed, I'm 99% confident this is German only.