The Wii U is setup in a similar way to the original Nintendo DS, and will use the required language that is set in the Wii U settings: This option was mainly used in European releases, but there are American and Japan releases that do this as well.
However, some games will run the game in the required language that is based on the language that has been set in the BIOS.
Since the Nintendo DS is a region free device, it means you can inject any Nintendo DS (.nds) rom you like, regardless of the Game ID inside the game.
