sdfa.js

var rootFolder = $firebaseObject(FolderService.getFolders($scope.courseID));
//reference to rootFolder is created and can be used, once the data is loaded
//it will show up in scope
//or wait till loaded like below
rootFolder.$loaded().then(function(){
  //do stuff with rootFolder
})
...

getFolders: function(courseID) {
        return new Firebase(FirebaseUrl).child("folders/" + courseID);
      }