The windows app has been out for 18 months. We are busy and keeping the iOS, OS X, JS and ruby versions of our application is enough!
The application works with spotdox.com and can be downloaded now from http://spotdox.com
We have an OS X app written in objective - C that you will use for reference to add features and fix bugs.
You need to understand web services, threaded app (the C# app is heavily threaded) and be able to create installers for windows.
We also have some other C# windows app development projects. Everything is for Windows 7 or later.