Fair Use May Shield LLM Training Using Copyrighted Materials, But Output Infringement Likely Is The Next (Better?) Battleground

To date, most efforts to challenge what LLMs like GPT-5, Claude, Llama, Grok, and Gemini, among others, are doing with copyrighted materials have focused on inputs used to train these models. However, the ongoing case involving Anthropic's Claude model (Bartz v. Anthropic) is the most recent illustration - and most prominent - that courts are likely to find LLM training on 'legally obtained' copyrighted materials to fall under the 'fair use' exception to copyright law. Challenging the use of copyrighted materials for training LLMs has its benefits. There are numerous authors, publishers, artists, and more who have had their materials used for such efforts, and challenging the training coalesces these groups to fight these training efforts. One benefit, if these groups prevail, is that any output likely would not include their copyrighted material because the LLMs would not be trained on that material.