Access to Main.cxx from custom Slicer Python application

We have a custom Slicer Python application that starts in Main.cxx and utilizes a main window specified in xxxAppMainWindow.cxx (both files originally developed by Julien Finet, Kitware, Inc.) I want to modify/add to this part of the code in order to facilitate license management via a simple modal dialog. I have the following questions:

  1. Is there complete access to Qt at this stage of execution i.e. can I create and use something derived from QDialog?
  2. What is the scope of this dialog (from 1.) i.e. will I be able to instantiate it and render it from the custom application Python code? If so, how is it exposed and referenced?