Use angular.injector. Using your code you can do something like the following:
angular.module('main.app', []).factory('MyService', ['$http', function ($http) {
return new function () {
this.GetName = function () {
return "MyName";
};
};
}]);
angular.injector(['ng', 'main.app']).get("MyService").GetName();
Here is the jsfiddle: http://jsfiddle.net/wGeNG/
NOTE - You need to add "ng" as your first module before loading your custom module since your example code depends upon $http provider which is in the ng module.
EDIT - Using get() as in OP's answer but note this code is fetching the service without relying upon the element being bound to the app module "main.app".
