Read the Order, which is Exhibit B to Antrhopic's appellate brief.
Anthropic admitted that they pirated millions of books like Meta did, in order to create a massive central library for training AI that they permanently retained, and now assert that if they are held responsible for this theft of IP it will destroy the entire AI industry. In other words, it appears that this is common practice in the AI industry to avoid the prohibitive cost of paying for the works they copy. Given that Meta, one of the wealthiest companies in the world, did the same exact thing, it reinforces the understanding that piracy to avoid paying for their libraries is a central component of training AI.
While the lower court did rule that training an LLM on copyrighted material was a fair use, it expressly did not rule that derivative works produced are protected by fair use and preserved the issue for further litigation:
Again, Authors concede that training LLMs did not result in any exact copies nor even infringing knockoffs of their works being provided to the public. If that were not so, this would be a different case. Authors remain free to bring that case in the future should such facts develop.
Emphasis added. In other words, Anthropic can still face liability if it's trained AI produces knockoff works.
Finally, the Court held
The downloaded pirated copies used to build a central library were not justified by a fair use. Every factor points against fair use. Anthropic employees said copies of works (pirated ones, too) would be retained "forever" for "general purpose" even after Anthropic determined they would never be used for training LLMs. A separate justification was required for each use. None is even offered here except for Anthropic's pocketbook and convenience.
...
We will have a trial on the pirated copies used to create Anthropic's central library and the resulting damages, actual or statutory (including for willfulness). That Anthropic later bought a copy of a book it earlier stole off the internet will not absolve it of liability for the theft but it may affect the extent of statutory damages. Nothing is foreclosed as to any other copies flowing from library copies for uses other than for training LLMs.
Emphasis in original.
So to summarize, Anthropic apparently used the industry standard of piracy to build a massive book library to train it's LLMs. Plaintiffs did not dispute that training an LLM on a copyrighted work is fair use, but did not have sufficient information to assert that knockoff works were produced by the trained LLMs, and the Court preserved that issue for later litigation if the plaintiffs sought to bring such a claim. Finally, the Court noted that Anthropic built it's database for training it's LLMs through massive straight-up piracy. I think my original comment was a fair assessment.