First off, I am not a lawyer but have consulted them. A lot of this is a gray area and not well defined. As you mention, there is the code, the given models, models fine-tuned on those models, models trained from scratch, using styelgan reimplementations, etc. Even with the license being included there does not mean that the output of a model trained from scratch counts as derivative work. And technically I just sell things like upscaling, keeping images private, google sync etc and provide unlimited image creating for free (not sure if that would hold up in court but I think it's relevant). So, no I do not think I am violating the license. But some lawyers may feel differently.
Also, I try hard to cite everything involved. Google was thrilled by my use of the biggan model and how it showed off the model. With the amount of money I have spent on Nvidia cards, I hope they are happy too :)
and then image ownership is a whole other question. Everything in arbreeder is CC0 to keep things simple https://artbreeder.com/terms.pdf
Best, Joel