Oh, that's way more interesting. So they have standing? I can see the argument that altering the execution of the program sent to the users computer is a DMCA violation (i vehemently disagree, but i can see it). But i don't think they didn't actually wrote the page that's delivered to the user.
I'd imagine it would technically need to be the publisher or the agent that took legal action. This was clearly an experiment though. Expect much more widespread use and, I'd assume, a court case soon.