The patent on the lockout mechanism has expired and clean software implementations of the algorithm have been created. So the old legal protections no longer apply.
And while Nintendo still aggressively enforces their copyright on their old games, they probably don't care very much about unlicensed games being created for their very old hardware. It's just not commercially relevant to them.
And while Nintendo still aggressively enforces their copyright on their old games, they probably don't care very much about unlicensed games being created for their very old hardware. It's just not commercially relevant to them.