Do Models and Services *have* to extend Actor? why?
No! You don't have to extend anything in RL - the mvcs package is just a reference implementation that provides some handy wiring (usually just oft-needed dependencies).
Robotlegs is simply an "automated" (or managed) dependency injection framework. Actor, for example, just declares a dependency on an EventDispatcher and provides a helper method - you could do this yourself with any Class without having to extend anything.
So, Actor gives you 3 handy things:
It depends on the context EventDispatcher
It creates an EventMap that wraps that EventDispatcher
It defines a dispatch() helper method
If you choose not to extend Actor, you just need to decide if you want any of those things, and then set them up yourself in your Class if you wish.