Whoever operates the LLM, in this case OpenAI, engaged in copyright infringement through the unauthorized modification, reproduction and distribution of content to you.

> sure, but if I use an LLM to write a novel/article, I can be sued in civil court not the LLM

That's function of the legal system, not of the technology. If tomorrow someone made a perfect dolphin-Esperanto translator and proved Dolphins were as smart as humans, you still can't sue a dolphin until the legal system says so.