[Answer]-Django form subclass non-functional

That’s not how you customise a class based view. The third parameter in a urlconf is for parameters that are passed as part of the request, alongside those captured from the URL itself: it’s not for configuring the class view.

To do that, you should either override the class in your code and set the attributes there, or you can pass them as parameters to the class’s as_view() method:

url(r'^register/$', RegistrationView.as_view(form_class=CustomRegistrationForm, backend=registration.backends.default.DefaultBackend), name='registration_register'),