It may be counterintuitive at first, but why wouldn't be possible? It's one of the perks of "offline" hardware without subscriptions or DRM. You build a piece of hardware (cartridge) that attaches to another one (console) and it works. As long as the console works, there shouldn't be a problem.
Nintendo is notoriously litigious.
> It may be counterintuitive at first, but why wouldn't be possible?
For the same reason it wasn't possible at the time for a third-party to make N64 cartridges themselves to avoid Nintendo's fees. But I assume these lockout chips are replicated or circumvented by now.
Agree. There is a wall coming for "retro" video game nostalgia once we reach the end of the purpose-specific hardware era. Like, you can build an emulator for WiiWare games, but what does it mean to release a "new" WiiWare game when they're just built using an API like OpenGL which is still being used in new games today? What does following the constraints of an older system like that result in besides just another, lower, quality setting? What does "retro" Fortnite look like in 10 years besides just worse shaders?