Assuming you're referring to Stable Diffusion, the training set photos are not used commercially. Using them in training is non-commercial. If they were to share the training set, that would be commercial. However, the final product (the neural weights) does not include any of the training data and so there is no commercial use of your photos occuring.

It's the same as if I were to look at your photos and then take my own similar photos for the background of a web store. I would have "used" your photos in some sense. But I would not have used them commercially in any way whatsoever.

You have just as much grounds for complaint in Stability's case as you would in the case of me looking at your photos as reference for my own.

Commercial use isn't required for copyright infringement.

Regardless, there is no copyright infringement occurring when I use my memory of having seen someone else's copyrighted materials to produce my own wholly new but similar looking works.

Likewise there is no copyright infringement occurring when an ML model is trained on copyrighted works.

Stable Diffusion is a 5GB matrix of floating-point numbers trained on 240TB of data. It does not, and cannot, contain infringing data from the training set. It is physically impossible for it to contain such data. There is not, and cannot be, any infringement occurring.

> ... when I use my memory of having seen someone else's copyrighted materials to produce my own wholly new but similar looking works.

That's called "non-literal" copyright infringement. Plaintiffs win on the claims and appeals courts uphold the judgments. (See, e.g., the "Blurred Lines" case. https://www.nbcnews.com/pop-culture/music/robin-thicke-pharr...).

A person could infringe the copyright in an original image if they painted their own version by hand. The AI is basically irrelevant.