Hello @Sz380230439fvv,
For any of the products using generative AI features (such as Firefly web site, Ilustrator, Photoshop, Adobe Express) these are the guidelines for use: Adobe Generative AI User Guidelines. These guidelines say that content created with generative AI features can be used for commercial use unless the product is in beta and it says it cannot be used for commercial use. The only other thing to note is if you are using the free Firefly plan, you cannot remove or crop out the watermark, even if your use is noncommercial/personal only.
Whether Adobe says it is commercially safe to use and whether the use of an image presents any legal or intellectual property issues are different questions. On whether it is acceptable to use an AI image on a book cover based on intellectual property issues (copyright, do you actually own the image, can you licence the image to the publisher, etc.)—these are legal questions that are best answered by your legal counsel. This area of the law is in flux and ambiguous, and different based on region. If you need to make business decisions based on the answer, it is best to talk to your attorney.
My best,
droopy