I can't take a project described as a "JavaScript framework" serious these days. A framework for _what_? Many things are done with JS nowadays.
The tagline says it all, really. I never used it myself, but their examples seem to go a long way at explaining the philosophy.
The framework vs library debate is a boring one and goes nowhere.
However, the project tagline on Github (but not the docs), which is but one click away, states “A rugged, minimal framework for composing JavaScript behavior in your markup.”