NOTE: Haven't used AngularJS and only scraped the article. But Rails for example, doesn't have a namespace problem, because ruby modules provide a namespace and prevent name clashes easily.
That said, I'm not sure Rails and AngularJS are direct competitors as many apps use a combination of both frameworks or more generally Rails + JS-framework.
Rails and Angular are apples and oranges. Angular isn't a full-stack framework, it's a client-side framework that handles data source interfacing and view updating.
Rails doesn't have a namespace because Ruby has namespaces and Javascript doesn't - it'll be added in ES 6. Rather late, I think, but there you go. You can actually fake namespaces with Angular if you use a module framework like Require.js, but that involves adding more boilerplate to every module (like Angular 2.0 will actually require as well).
That said, I'm not sure Rails and AngularJS are direct competitors as many apps use a combination of both frameworks or more generally Rails + JS-framework.