We aren't the target market here. We not only are veteran D&D players, we know enough to look at 3rd party materials, regularly discuss the game online with fellow players, and many of us go to gaming conventions or even write our own materials. We're a little beyond "dummies". This book is pretty clearly for somebody who has heard of D&D, is vaguely interested in what it actually is, but is too daunted by normal channels to get into the game.
If somebody who knows only the vaguest things about D&D (It's a game with elves and wizards and stuff, and it's kinda like Lord of the Rings), and they walk into the RPG section of their local chain bookstore, they're not going to know what to grab first. Hmm, "Basic Game", sounds like a place to start, but "D&D Miniatures Starter Set" also sounds like something to start with, or maybe "Player's Handbook" since I want to be a Player, or "Epic Level Handbook" because I'd like to play something epic like LotR.
". . .For Dummies" is a trusted brand for demystifying the obscure, which D&D can be to an outsider. The "Dummies" books are also shelved separately from gaming books, which means people who might never look at a D&D book will see this book and have a chance to pick it up and consider the hobby. Some people might pick it up out of curiosity, and find that they had big misunderstandings about what the game is and a few might even take up the hobby.
If the book explains the basics of the playing the game, what books they need to buy first, and how to enter the Gamer subculture, then it works.
As for not putting any d20 products or ENWorld on their resources list, realistically that would never happen. Explaining the d20 market and license to a total newbie is another layer of complexity that could be avoided in an introductory book, and if they were going to list a web site it would be
http://www.wizards.com. WotC is in it for the money, they aren't going to direct anybody to anything they aren't going to directly make money off of.