So if I'm reading this correctly:

• The first clause just means you can't scrape all the content on their site into siterips and then make that siterip available for others to download (TOS 24(d)(9))
• The second clause means that if users tag their content with "NoAI", then Epic/ArtStation promises to not use that content in training their own AI models. (TOS 46 para 1, 2)
• The third clause means they (Epic/ArtStation) won't allow/license third parties to use your content (whether tagged as NoAI or not) in training the third party's AI models (TOS 46 para 3)

To my untrained eye, it looks like they are just covering themselves from the situation where someone rips the entire site's contents and feeds it into a model, and then the copyright owners of the ripped work, i.e. their users, complain that this was done without their consent. Interestingly enough they still allow themselves to create models using their users work unless the users explicitly opt-out.

Unless I'm missing something completely, this doesn't prohibit you from uploading AI generated works just because they are AI generated. However any copyright claims over having used someone else's works without their express permission would of course overrule that.

It's quite interesting as to where the line is.

The situation is much more nuanced than the old cases of artists literally tracing over someone else's linework versus merely using it as inspiration without mimicking everything down to the exact pose. Even if you were to liken the AI models to glorified autocomplete engines for linework that compares tens of thousands of images and then uses statistics to generate a new image using a small percentage weighting of each image, how does this compare to an artist whose works are the result of every other piece of art and media he has seen in his life? Someone might say it is the difference between a machine just adding up equations versus a human using "creativity" and "imagination", but how different is that really?