Awesome

Async GIF decoder

An asynchronous GIF decoder written in ActionScript 3 that lets you play animated GIFs in flash without freezing the UI.

Inspired by Lee Burrows' Async-Image-Encoders, based on Thibault Imbert's as3gif.

var gif:GIF = new GIF();
    gif.addEventListener(Event.COMPLETE, function(event:Event):void
    {
        trace("done", gif.totalFrames);
        gif.play();
    });
    gif.addEventListener(IOErrorEvent.IO_ERROR, function(event:Event):void
    {
	    trace(event);
    });
    gif.load(new URLRequest("smile.gif"));

addChild(gif);

If you want to play GIFs in your starling based app, you can use renderers/GPUGIF class.