It does not use any of the Nintendo licensed code or parts and as such is not valid target for DMCA claim?
You can run homebrew un-copyrighted ROMs just fine. Should this be DMCA claimable then I guess all video players (VLC) should be too by that logic, because you can play copyrighted content on them.
Knowing Nintendo, they will try. Since you can actually run copyrighted roms. (I dump all my roms from original cartridges using the Epiloque Operator. (see https://www.epilogue.co/) and then copy them over using iTunes on Windows)