Microsoft asks court to deny authors summary judgment, arguing LLM training is fair use "as a matter of law"

Microsoft filed a 54-page brief on Oct. 23, 2026 (Dkt. 2173, public redacted version) in the consolidated author copyright cases against OpenAI (In re OpenAI, Inc. Copyright Infringement Litigation, S.D.N.Y. No. 1:25-md-03143), opposing the class authors' motion for partial summary judgment. Microsoft argues that training a large language model is fair use as a matter of law -- "an LLM is not a book machine. It is an everything machine" -- and that OpenAI's LibGen and Books3 downloads were transformative because their purpose was to tokenize books for training. It also says it did no downloading itself and cannot be directly or vicariously liable, and that the authors show no lost sales and no cognizable market for training licenses. The court has not ruled.