And for both, DC, and GameCube. Youll need to ask the preowner if he/she has deactivated the account. If they haven't, that's your problem. That's the prob with purchasing used online games. =\
Hope everything works out!
Its a risk but unlikely that the gamecube version would have a used serial key etc if its second hand. With the dc u just went online simple with the gc version ud have to spend £30-40 for a modem or bb adapter doubt many people would spend that on one game just to trade it in for £15. Suppose if oyu cant find a new 1 the risk is up 2 u.