For anyone interested, here are the steps I followed to generate the swf file with the MTASC compiler.

MTASC mainly complained about code in the class YouTubePlayer, which is instantiated in the YourTubePlayerWrapper class.

The compiler objected to the global functions removeMovieClip and unloadMovie. I replaced these with the instance method calls,
(parent[ players ]).removeMovieClip(); and ( parent[players ]).removeMovieClip();

The compiler did not like mx.utils.Delegate, so the various calls to the Delegate.create function created a problem (in both the YouTubePlayer and YouTubePlayerWrapper classes).
Apparently, most of the mx components, including mx.,utils.Delegate, are not directly supported by MTASC. After removing all references to the mx.utils.Delegate and any calls to its create method, I add the following class and replaced calls to Delegate.create with calls to EventDelegate.create:

class EventDelegate {
private function EventDelegate () {};

public static function create (scope, method:Function):Function {
var params:Array = arguments.splice (2, arguments.length-2);
var proxyFunc:Function = function ():Void {
method.apply(scope, arguments.concat (params));
}
return proxyFunc;
}
}

(see: “http://lists.motion-twin.com/pipermail/mtasc/2005-April/001602.html”)

Lastly, MTASC complained about the following syntax in the loadVideo function:

loader.addListener({ onLoadInit: loadInit() });

I replaced this with:

loader.addListener(this);

and changed the name of YouTubePlayer’s loadInit method to onLoadInit.

After these changes I was able to use MTASC to generate YouTubePlayerWrapper.swf.

Is there a better way to create the swf file?