The only legal way to do that in the proprietary software world is a clean room implementation.
An AI could never do a clean room implementation of anything, since it was not trained on clean room materials alone. And it never can be, for obvious reasons. I don't think there's an easy way out here.
Google's engineers when they were copying Java API for Davlik (and later ART), they had access to and consulted Java source code. The infamous Oracle v. Google judgement siding Google set precedent at the highest level, SCOTUS that looking at the code is not an issue.
So, it doesn't matter if a AI can or cannot do clean room implementation. Unless it is a patent or trade secret violation, cleam room implementation doesn't matter.
An AI could never do a clean room implementation of anything, since it was not trained on clean room materials alone. And it never can be, for obvious reasons. I don't think there's an easy way out here.