That's interesting to know, but that doesn't by itself imply that it's illegal. For example, Google Books, which has massive amounts of scanned PDFs of copyrighted works, is considered fair use under US copyright law.
It's fair use if the work is "transformative". GPT-4 isn't publishing the content of the books, it's publishing a model derived from the entire corpus. I'm not a lawyer, but I think there's an argument that it is transformative.
It's correct that OpenAI isn't publishing any of the "stolen" content directly. But they "stole" it to make their service possible in the first place. Not distributing it themself doesn't make much difference than.
