I feel like the standard "Free as in Gratis vs. Free as in Freedom" argument doesn't quite explain the issue people have here.

Open-source code still had terms, and AI training was an unfortunate blind spot in those terms. If a human being learned how to code 100% from open-source code, nobody saw a problem if that person went on to write closed-source code.

But it feels fundamentally different when the open-source code is just being fed into a machine that uses absurd amounts of processing until closed-source code comes out the other side. It feels like theft.