I think originally Apple was using SproutCore, which had similar aspirations to produce "desktop quality" web apps, and was one of the early frameworks to implement things like two-way data binding. This was back when iCloud was called MobileMe.

SproutCore 2.0 became Ember.js 1.0, but I don't know if Apple are still using it.

Cappuccino was not an Apple project, so I doubt that is what Apple used to develop those projects. That, and 280 North eventually got acquired by Motorola.