Free, cross-platform 2D game engine powered by Haxe and OpenFL

MIT License

flixel

flixel-ui

Embeddable, in-game editor for HaxeFlixel. Turn the existing Flixel debugger into a full-featured editor!

flixel-studio

flixel is a free Actionscript (Flash) library that I distilled from a variety of Flash games that I've worked on over the last couple years, including Gravity Hook, Fathom and Canabalt.  It's primary function is to provide some useful base classes that you can extend to make your own game objects.