If the AI is good enough to truly implement the whole thing to a similar level of reliability without copying it then who cares. At that point you should be able to decompile any program you want and find enough information inside that an AI can go write a similar quality program from the vague information about the call graph. We've transcended copyright in computer code.

If it can't and it costs a bunch of money to clean it up then same as always.

OTOH if what is actually happening is just that it is rewording the existing code so it looks different then it is still going to run afoul of copyright. You can't just rewrite harry potter with different words.

Note that even with Google vs oracle it was important they didn't need the actual code just the headers to get the function calls were enough. Yes it's true that the clean room isn't required but when you have an AI and you can show that it can't do it a second time without looking at the source (not just function declarations) that's pretty strong evidence.