Buying games from Sprocket games store is just like having a hard disc. Copy it to any media you want and you can install it from there with the key they email you. Game is always available to download again in case your chosen media fails or is stolen or lost.
Also buying it from Sprocket Games is buying direct from the developer. Buy direct and save, especially when the digital copy is just like having a dvd copy... no 3rd party stuff to install or run on your computer ie "STEAM"