From the weekly Nintendo PR:
Basically, if you got a toy and the base, you can simply download the game for free on the eShop. If you can get that stuff from a friend, you can get a free copy of the game.
Disney Infinity For the first time, Disney Infinity is available in the Nintendo eShop and its free to download. Enjoy online multiplayer and more fun ways to play. Use your Wii U GamePad controller to create your own worlds in the Toy Box or activate missions and unlock toys in Play Sets. With Disney Infinity, the possibilities are endless. (A Disney Infinity Figure and Base, sold separately, are required to play the downloadable version of the game.)
Basically, if you got a toy and the base, you can simply download the game for free on the eShop. If you can get that stuff from a friend, you can get a free copy of the game.