As described, this would not be the same thing. If the AI is looking at the source and effectively porting it, that is likely infringement. The idea instead should be "implement Minecraft from scratch" but with behavior, graphics, etc. identical. Note that you'll need to have an AI generate assets or something since you can't just reuse textures and models.

This was not about legality.

> That question is this: does legal mean legitimate?

Just because something is legal does not mean it's moral thing to do.

I’ve often thought that the key to fighting this is through this exact method. Turn the tool against them

The big question is: if copyrighted material was used in the training material, is the LLM's output copyright infringement when it resembles the training material? In your example, you are taking the copyrighted material and giving it to the LLM as input and instructing the LLM to process it. Regardless of where the legal cards fall, this is a much less ambiguous scenario.

You will probably run into design patents.

They might not care. Products win not by quality or features but by advertisement, hype and network effects.

The original implementation would still have the upper hand here. OTOH if I as a nobody create something cool, there's nothing stopping a huge corporation from "reimplementing" (=stealing) it and and using their huge advertising budget to completely overshadow me.

And that's how they like it.