If I hired a human to write a clone of GNU grep to be released under a MIT license, and he wrote one that was performed exactly the same as GNU grep, it would be impossible for me to prove that the guy I hired didn't look at the GNU code.
But we'd be able to look at his clone code and see it's different, with different algorithms, etc. We could do a compare and see if there are any parts that were copied. It's certainly possible to clone GNU grep without copying any code and I don't think it would fail any copyright claims just because the GNU grep code is in the wild.
If that was the case, the moment any code is written under the GPL, it could never be reimplemented with a different license.
So instead of a human cloner, I use AI. Sure, the AI has access to the GPL code - every intelligence on the planet does. But does that mean that it's impossible to reimplement an idea? I don't think so.
