I'm sure that's worked out ahead of time and not dependent upon ticket sales. This fest obviously is having trouble selling tickets (did last year as well) and may be strapped for cash trying to get this thing off the ground. Part of me thinks that TR/MMR being fans of these types of art installs may support it by taking less.
On the Thom Yorke discussion; I found some pictures of the Blue Stage area from last year
(festival map). looks like a good amount of space, but it's a really long space and easy to wind up waaaay in the back or stuck on the side.