How close can you get to a verbatim work if you train on an author's style and provide detailed chapter summaries?
If it could produce a close to verbatim copy of a work that had not been written when the model was trained would it still count as a copy.
I feel this would be a continuum that extends either direction.
Consider the thought experiment of a hypothetically smart model that knew all of an author's work and a detailed background of the author's experiences and psychology. If you ask the model to write a sequel to "Not that Jenny" and it produces a verbatim version of what the author will write next year, does it count as a copy?
Put aside the notion of whether you think this would ever be possible, think of how you would consider the book if you found a model had succeeded in this task.
Going in the other direction you have a model that has been trained in an author's style with very little in the way of knowledge or reasoning, barely more than the ability to speak and an understanding of idioms and structures that the author might use. This can't write a complete novel but it can correctly guess the next word of a novel 99% of the time.
If you have a map of the 1% of words it gets wrong, you can reproduce the novel from a very small amount of information. Would you say that the model contained the novel, or would you say that the word error list was a compressed representation of the novel and the model did not contain the novel.
This is where things get difficult to quantify what exists 'as a copy' in a generative model.
Surely it would be reasonable for a model to know an outline of what happens in a story. If it knows the outline and style, I don't think that would count as containing the copy. As you increase the ability of the model to infer, and increase the information that it holds to the point that it can reproduce verbatim does it contain a copy? What about if you reduce the ability to infer back to where it was earlier and it can no longer reproduce the novel, does it now not contain the novel? Even though the amount of information about the novel has not been descreased, just its ability to infer, it can never produce a verbatim copy.
In the end I think the notion of whether the model represents a copy in itself becomes too nebulous to be meaningful. It's like an artist who can draw a copyrighted work from memory. They may be able to commit copyright violation but they themselves are not a copyright violation simply for having the ability.