That's the million dollar question for so many hardware and software projects where the information is linked to some page that says nothing about what it is or what it does including the github link to its creator here.
I haven't been following the scene too closely, but there's been a huge ecosystem of fpga clones of 90s video game consoles in the last few years. The "mister" project is one such endeavor.
The market for the original hardware, old cartridges and mods for things like better video signals or Bluetooth controllers is also popping.