Obviously restricting the input will cause the model to overfit, but that’s not an issue for most models where Billions of samples are used. In the case of stable diffusion this paper had a ~0.03% success rate extracting training data after 500 attempts on each image, ~6.23E-5% per generation. And that was on a targeted set with the highest number of duplicates in the dataset.

The reason they were sold doesn’t matter, as long as the material isn’t being redistributed copyright isn’t being violated.