Those instructions you're referring too. They actually describe what the Model and Controller will do. You only need to paste the code into the correct file.
It is Griffon 0.9.1 (not 0.9.0) the one that will not work on Windows platforms. There two additional releases after 0.9.1 that deal with the problem.
Could you please post a stacktrace with the CNFE error?
A Griffon application is made of MVC classes. When you create a new application using the create-app command, Griffon will create a dummy MVC triad, named according to your application name. If your application is called DemoConsole, you'll have :
The DemoConsole is a simple application having a textarea, where you'll write groovy script. It also has a button to evaluate the content of the textarea and show the result in a label. All components are defined in the DemoConsoleView. The DemoConsoleModel holds the values of the view (the fields are binded to the UI). The DemoConsoleController does the job of evaluation the script when the button is clicked.