How we built the Waifu Vending Machine
The dataset this is built from (https://www.gwern.net/Danbooru2018) is, simply put, copyright-infringing on a gross scale. The vast majority of the images uploaded to 'boorus' completely lack a compatible license or the artist's express consent. The redistribution via torrent of 2.5 TB of some 3 million images only compounds this problem. None of this is ameliorated by the $20 'generosity' of the dataset creator.As a result, every single artist whose work was included in that dataset has a clear, meaningful claim that each and every 'waifu' sold ($20, if customized, or $5 if random) by Sizigi Studios is an infringing derivative work. Coupled with at least one of the project authors' ready admissions -- in this very comment section -- of scraping image sites himself, I would say that this team is playing with fire. Even in the case that an algorithm's output is somehow found to be 'creative' rather than mechanistic, AND this specific application is found to be in all cases substantially transformative, there's STILL the original massive 2.5 TB of copyright infringement up front to deal with.All an enterprising lawyer would need to begin is to search the BigQuery metadata for the 'artist' and 'copyright' tags on these images.  Note of course that the 'copyright' tag is widely misused on boorus and similar image repositories to refer to the inspiring franchise; 'trademark' would be much more accurate descriptor.EDIT: 
I do not mean to suggest that litigation from the use of the dataset in this ML (as opposed to the original, clearly infringing, download & redistribution) would in any way be an easy, one-sided case --- only that this scenario would represent nearly the worst possible test case imaginable for determining the future legality of ML, short of directly antagonizing the RIAA or MPAA.