I would actually love it if that was true. It would reduce a lot of legal headaches for sure. But if that was true, why were previous GPT versions not as good at understanding language? I can only conclude that it's because that's not actually true. There's not enough digital public domain materials to train a LLM to understand language competently.

Perhaps old texts in physical form, then? It'll cost a lot to digitize that, wouldn't it? And it wouldn't really be accessible to AI hobbyists. Unless the digitization is publicly funded or something.

(A big part of this is also how insanely long copyright lasts (nearly a hundred years!) that keeps most of the Internet's material from being public domain in the first place, but I won't belabour that point here.)

Edit:

Fair enough, I can see your point. "Surely it is cheaper to digitize old texts or buy a license to Google Books than to potentially lose a court case? Either OpenAI really likes risking it to save a bit of money, or they really wanted facts not contained in old texts."

And yeah, I guess that's true. I could say "but facts aren't copyrightable" (which was supported by the judge's decision from the TFA), but then that's a different debate about whether or not people should be able to own facts. Which does have some inroads (e.g. a right against being summarized because it removes the reason to read original news articles).