I still don't understand what the value of specifying a license for generated images is - at least in terms of enforceability. How could anyone reliably, conclusively determine that an image was generated using a locally-run tool?

I suppose in the case of DALL-E they probably save a copy of every generated image and can use some sort of reverse image search and find if/when the image was created.

With StableDiffusion or any other local tool I don't see how that would be possible. The best I think one could do is come up with a secondary tool that can pinpoint the position in latent space a generated image came from (if that's even possible, I have a limited understanding of how exactly these systems work.) But then, if (heaven forbid) someone applied any sort of cropping or post-processing to the image, an approach like that easily gets blown out of the water.