For the 'legal' part... you're generally not allowed to install whatever arbitrary software you want on other people's machines without some sort of consent, even in an Apple store. I'm not sure how much more elaboration this needs.
For the 'moral' part... he's taking a small intimate chunk of a person's life without their knowledge or consent and putting it in a picture frame because he finds it interesting and enjoyable. The reason he gives for this is "art". There's not even slight consideration of the people involved other than he considers that intimate chunk of their life and likeness to be his personal medium for "art", the same way clay or watercolors might be to a less terrifying person. Again, there are far worse ways he could create 'art' via nonconsensual intimacy, but my point is that it's fundamentally amoral to use people in that way in the first place.
What's interesting about this is that in this community we read about security researchers that do illegal (but generally not unethical) things, and about large companies that do unethical (but arguably not illegal) things. This guy does the worst of both and somehow people seem to be on his side.