Hmm, before I go down this rabbit hole of googling: can you daisy chain these? Or does anyone know of projects/products where you can? Would be even more fun to have 2 or 4 player capability!
JoweWe were talking about this same thing. Think of the Raspberry Pi as your console. It has multiple USB connections on it. The joysticks actually plug into the raspberry pi via USB. So you should be able to run a USB out of the second joystick and connect it to the primary joystics raspberry pi and play 2 player. I have requested 2 samples from the vendor to test this situation as I want to be able to play contra 2 players!