#HumanAuthored is a project of The Authors Guild that allows an author to certify that their book is created by a human. Minor uses of #AItools, such as for spell-checking or research, are permissible, but the core literary expression must originate from the author. By signing the licensing agreement, authors affirm that their work meets these criteria.
It's a self-certification approach emphasizing trust in the author's integrity as an organized professional.

Similar initiatives include:

#C2PA Coalition for Content Provenance and Authenticity: a joint initiative formed by Adobe, Arm, Intel, Microsoft, and Truepic to develop technical standards for certifying the source and history (provenance) of media content.

#FairlyTrained: a non-profit organization that certifies generative AI companies for ethical training data practices. Their mission is to distinguish between AI companies that obtain consent from creators for their work used in training data and those that do not.

With thanks to Johan Cedmar-Brandstedt for the insights.