You're coding against the concrete implementation of EventDispatcher.
This means that everything MUST extend EventDispatcher to work with
EventController. Fortunately, nearly everything (especially the native
flash lib) does. It is possible thought to not extend EventDispatcher
and instead implement the IEventDispatcher interface. Coding against
the interface will allow you to work with both cases, and should not
introduce any regressions (EventDispatcher just implements the
interface).
Thanks