Nice effect. But it is interesting how "lightweight" is used here. Sure, the library might be lightweight, but the CPU usage of my Chrome instance jumps to nearly 100% as long as I play with the demos. That's not "lightweight" for the user.
I can't remember right now, but I saw a similar background on some website where they had put the blurry demo of the website in the background and moving the mouse over it kept it un-blurring. Looks nice!
Seems interesting, will give it a try tonight. Thanks for sharing!