The assumption here is that if the artist de-legitimises their art then it ceases to be art. not sure if that would work. If the artist de-legitimised it then it could continue to be auctioned on a regular basis and the artist would just stop receiving their 15% cheques.
Mind you if the software is custom and maintained by the artist...
Yes, it sounds like it is not totally self-contained:
The software driving the project will remain hosted on servers of the Artist’s choosing to aid in maintenance. Artist will supply a copy of the software upon request by either the Collector or any New Collector.
So he could potentially stop it from continuing to sell itself, although of course it could still be sold, or modified so that it started to sell itself again without his permission.