Access to Product Source Code
Wing Pro licenses includes access to product source code, with a signed non-disclosure agreement. Source usage rights are summarized as follows:

You may make alterations and improvements to the source code as long as you don't try to defeat our license validation code or remove our copyright or trademark.
You may distribute any changes you make to the source code, in the form of patch files or in other forms that don't include substantial parts of our code. These can be open source or commercial at your discretion, and we have no special rights to them.