Also above the fold: "AngularJS is a toolset for building the framework most suited to your application development"...
Even internally they're insecure about it. I think library is a more useful definition because it encourages developers to think about architecture before they start building application specific stuff.
From their own project page: "AngularJS — Superheroic JavaScript MVW Framework" (empasis mine).
You have to code your logic inside its objects (controllers, directives, services, etc) -- that's not how a library works.