The problem was never in the "left," but in the "copy." Copyleft was a hack that Stallman and many others built on top of copyright law — software-freedom copyleft sits on copyright. So when copyright law breaks, the public licence breaks with it, because the workaround you mention also applies to proprietary code: It only applies to particular instances of copying. And now most large language models — one major family, from Claude 4 onwards — no longer recite verbatim from the corpus. They do ingest the bank of scanned books — there are a great many physically scanned books in the training — but they maintain an index, a hash, so that whenever the model finds itself reciting more than, say, a sentence from a book, it stops itself. They used these during training, and the more advanced systems no longer reproduce that material verbatim, which means that, in most jurisdictions, they circumvent copyright law, which really only protects against reproduction in publishing.