This project is born out of the frustration with the Version 2 Component framework that shipped with Macromedia Flash Professional 2004.
ActionStep will include a full Responder architecture (NSResponder, NSApplication, NSWindow, NSView, etc) and be heavily based on delegation (rather than inheritance). The brilliant separation of concerns in AppKit will enable theming that is purely coded in ActionScript without requiring the Library of symbols. With ActionStep, you will be able to compile into a base movie the ActionStep classes that you use + customized theming classes, and any other movie that you load that uses ActionStep will 'inherit' those themed components at runtime. This will enable VERY SMALL flash movies that provide the much vaunted Rich Internet Application experience.
check it out (pre-alpha)
http://actionstep.org/