Nintendo's patent on their NES and SNES systems ran out in 2005, so apparently these knock-off combos are legal to play the carts on.

Q: Are RetroDuos allowed for use in score submissions? If so, this would open up new opportunities. If not...oh well. Seems like a good way to keep playing those old Nintendo system carts.



"Thank you, Mario. But our princess is in another ca--Mario, you look awfully green and spiny today! Are you oka--Wait a minim! You aren't Mario; you're...Yikes!"
[Beware of dopplegangers...]
:x