I don’t necessarily fault OpenAI’s decision to initially train their models without entering into licensing agreements - they probably wouldn’t exist and the generative AI revolution may never have happened if they put the horse before the cart. I do think they should quickly course correct at this point and accept the fact that they clearly owe something to the creators of content they are consuming. If they don’t, they are setting themselves up for a bigger loss down the road and leaving the door open for a more established competitor (Google) to do it the right way.
Eventually these LLMs are going to be put in mechanical bodies with the ability to interact with the world and learn (update their weights) in realtime. Consider how absurd your perspective would be then, when it'd be illegal for this embodied LLM to read any copyrighted text, be it a book or a web page, without special permission from the copyright holder, while humans face no such restriction.
No, there is no clause in copyright law that says "unless someone remembered it all and copied it from their memory instead of directly from the original source." That would just be a different mechanism of copying.
Clean-room techniques are used so that if there is incidental replication of parts of code in the course of a reimplementation of existing software, that it can be proven it was not copied from the source work.