Flash ActionScript Inheritance

So I am trying to figure out the following piece of code:

[as]

in Application.as
import Log;
class Application
{
private var _log:Log; // force mtasc to compile Log.as

function Application(createdBy)
{
// Re-assigment of _root to Application instance
createdBy.__proto__ = this.__proto__;
createdBy.__constructor__ = Application;
this = createdBy;

setup();
}
public function setup()
{
TRACE("hello world");
}
public static function main(createdBy:MovieClip)
{
var app = new Application(createdBy);
}
}; // end of class

[/as]

found here:

http://www.osflash.org/pipermail/osflash_osflash.org/2005-August/002165.html

So far I have been recommended to read the following article:

http://www.quantumwave.com/flash/inheritance.html

The article well covers the subject of inheritance in Flash 5 and MX. My only concern is that as the article points out using inheritance in this way it will be only an overload to the application.
..to be continued