The HelloWorldCompiled application is a modification of the HelloWorld application. It's designed to show you how to integrate custom Objective-C objects into a WebObjects application.
The application's main() function is defined in HelloWorld.m. It's principal responsibilities are to create a server adaptor, create an application object, and run the adaptor so that it can pass information between the server and the application. It also creates an autorelease pool that simplifies the process of deallocating memory that's no longer needed.
A scripted application (like HelloWorld) automatically deallocates script variables when they're no longer needed. When you create components with compiled code (as in HelloWorldCompiled), you have to provide a method that will deallocate these variables when the object that owns them is itself deallocated. See the dealloc method in Main.m and Hello.m.