Interestingly, Ed Newton-Rex, the person hired to build Stable Audio, quit shortly after it was released due to concerns around copyright and the training data being used. He’s since founded https://www.fairlytrained.org/ Reference: https://x.com/ednewtonrex
Even for rightsholders with tens of millions to hundreds of millions of library items like images or audio snippets, the performance of the encoder or similar feature in text-to-X generative models is too poor on the less than billion tokens of text in the large repositories. This includes Adobe's Firefly.
It is also a misconception that large amounts of similar data, like the kinds that appear in these libraries, is especially useful. Without a powerful text encoder, the net result is that most text-to-X models create things that look or sound very average.
The simplest way to dispel such issues is to publish the architecture of the model.
But anyway, even if it were all true, the only reason we are talking about diffusers, and the only reason we are paying attention to this author's work Fairly Trained, is because of someone training on data that was not expressly licensed.