First of all: you should never edit the script in the "RGSS Web Kit" section (unless, of course, you are an experienced programmer and knows exactly what you are doing). You should only use those classes and methods, without editing them. Read the DOCS to learn what each class/method do.
Second: Yeah, all those scripts in the "Gus Forum" section AND the AWorks input library are needed for that small chat room. But GusForum is actually just a little example of what you could do with RWK... It's not really meant to be used in games. Of course one could use it, but one should work to make it better and more stable. You see, that's why I said in the first post: "this isn't a script for people who don't know RGSS. RWK gives you a way to get online, but it's completely up to you to make it useful".
Third: A server for RWK is any HTTP server. A server for GusForum, though, can be created using the GusForum Server Scripts, available in the first post.