multi-player GBA games

[spedmetal]

OK this is what I understand. I have read through the instructions on my GBA and I understand that some multi player games only need one player to have the game and the others can just download the game into there memory while other games all the players have to have a copy of the game. This is my question I have a game "wild Thornberry’s movie" and I have read all through the instruction for the game but it doesn’t say weather or not all player need a copy or just one. I have it linked with a GBA and a GBA SP and I am using the GBA link cable and I only have one copy of the game and can’t get the other player to come up. I am guessing this means I need 2 copies of the game right. Can any one tell me where I can find info on what games only need one copy to play multi? Thanks