And what law is your friend breaking?
What if it was a webpage or applet ?
I don't think is as obvious that is illegal but IMO the people wronged here are the poor Apple shoppers that become part of the art, the article is trying to justify why this is allowed (public place , already recorded by cameras) but who knows what a judge will decide. But this s not something for NSA/FBI to waste their time on.
Those computers should (but who knows) be reset to factory settings periodically.