This demo shows off using realtime server validation using some AJAX-like concepts in conjunction w/qForms new API methods.
If you try to use the "username" of "demo", "guest", "admin" or "dswitzer" the application will throw an error. This happens because this test template will send the results of the username field via a XMLHttpRequest post to a template on the server. The server will then look to see if the value exist in a list of user names and if it does will tell the calling template to throw an error.
This is the code that's being run on the server side.