It does look like an interesting library. It's weird that the community seems so small.

Here is Michael's blog: http://blog.bolinfest.com/

And the HN discussion from when it was first open sourced: http://news.ycombinator.com/item?id=924426

Compiler : http://code.google.com/closure/compiler/

Library : http://code.google.com/closure/library/ (UI / widgets)

Templates: http://code.google.com/closure/templates/