After sifting through Stamen's projects (lots of interesting stuff there), I found out that it Manetas actually "yoinks'd" Stamen's experimental "Splatter" Flash project and appropriated it for the Pollock game. He took it to a really nice place, but while he did credit Stamen's work in the HTML source, it probably wasn't very nice of him to "borrow" like that without full permission.

I feel that MoCo praise should go where due, don't you?

Agree with jws' comment,the original project can be found here: http://stamen.com/projects/splatter

After I gave her a brief bio on Pollock, my 9-year old daughter played with it a while and found it quite fun.