Example of using multiple Ember.Namespaces with a custom Ember.Resolver to reuse code between projects. Ember App Kit's resolver as another example: https://github.com/stefanpenner/ember-jj-abrams-resolver DefaultResolver docs: https://github.com/emberjs/ember.js/blob/master/packages/ember-application/lib/system/resolver.js

resolver.js

/**
 * Super namespace that all our libs and apps will live on. We also extend all
 * of the native Ember classes as well and exclusely use them that way so we can
 * alter the behavior in one place without needing to reopen the original class.
 *
 * We call the super namespace PS for Pivotshare, call it what you'd like.
 */
window.PS = Ember.Namespace.create();

// Create our custom resolver so we can have Ember look up classes on multiple
// namespaces
PS.Resolver = Ember.DefaultResolver.extend({
    resolveOther: function (parsedName) {
        var value = this._super(parsedName),
            childNamespaces = Ember.get(parsedName, 'root.childNamespaces');

        // If it didn't resolve to anything, let's see if it's on one of
        // the child namespaces
        if (!value && childNamespaces) {
            for (var i = 0, l = childNamespaces.get('length'); i < l; i++) {
                // Change the namespace (root) that Ember will
                // use to look it up on
                parsedName.root = childNamespaces.objectAt(i);

                // Call original method again, with this different namespace
                value = this._super(parsedName);

                // First match found, wins.
                if (value) return value;
            }
        }

        // If reached, no match was found.
        // Ember will take it from here
    }
});

// Extending the default Ember.Application behavior
PS.Application = Ember.Application.extend({
    // Here is where we tell Ember to use our custom Resolver, defined above
    Resolver: PS.Resolver,
    childNamespaces: null,

    init: function () {
        this._super();

        // Needs to be an array if one wasn't provided
        if (!this.get('childNamespaces')) {
            this.set('childNamespaces', []);
        }
    }
});

// Extending the default ObjectController behavior
PS.ObjectController = Ember.ObjectController.extend({
    // Add common helpers/properties/features you always use
});

/**
 * PS.Core lives common components, views, models, etc
 */
PS.Core = Ember.Namespace.create();

// Just an example from today, put on PS.Core
PS.Core.IndexController = PS.ObjectController.extend({
    firstName: null,
    lastName: null,
    fullName: '$firstName $lastName'.interpolate().readOnly()
});

// Notice we're creating an instance of our PS.Application and providing PS.Core
// as a child namespace so that IndexController will resolve.
PS.SomeApp = PS.Application.create({
    childNamespaces: [PS.Core]
});

// If we don't provide a PS.SomeApp.IndexController, PS.Core.IndexController will be
// used instead! wooohoo