The NES could not run unlicensed software. In fact, the NES arguably invented the App Store licensing model. Every console (save for the toploaders) has a locko

The NES could not run unlicensed software. In fact, the NES arguably invented the App Store licensing model. Every console (save for the toploaders) has a lockout chip that resets the CPU every second or so unless it's able to exchange encrypted data with a companion lockout chip in the cartridge. Nintendo used this to "protect" the US gaming market from games they didn't approve of. Technically, the Family Computer (Famicom) could run unlicensed software. It even had a BASIC interpreter and a keyboard controller. Nintendo realized their mistake very quickly, however, which is why the NES has a lockout chip and the disk add-on for the Famicom also locked out third-party disks. (Note that part of the system was the ability to buy blank disks and pay to download games onto them via a Disk Writer kiosk, hence why the disks were proprietary, not just the games.) A number of game developers in Japan found that to be a bit of a shock, from what I've heard.