I was working on a similar project a while back, to view Street View through various filters (B&W high-contrast, pseudo-cyanotype, etc.), but I did it by pulling a few hundred images and caching them, to avoid hitting it in real-time, which I thought might be a problem. Given that I see several of these not being taken down, though, maybe I was too cautious.
Fwiw, Cyano-View Copenhagen was my project (hit "[reload]" at the top/right for a new random view, or scroll down for concept blurb):
1. There's a documented API to fetch these images, but it's less convenient.
2. These demos make Google look good.
3. There's no potential to squeeze money out of the creators of these demos, because they aren't monetized in any way.
4. Shutting down people who are playing (relatively) harmlessly with their technology would hurt Google's community image.
5. The demos are of no practical use, so if Google breaks compatibility, nobody will care.
So if you look at the costs and benefits, it would be unwise for Google to crack down on this sort of thing. But if you started selling an iOS app that used this, I'd be shocked if they didn't smack you down.