The only definition for a true dragon in that book is on page 103, which shows a list of all true dragons published to that date, which is notably lacking in any kobolds, dragonwrought or otherwise.
I did, however, manage to find your definition elsewhere. It was in wikipedia. Not really the place to go for D&D rules disputes.
Really this whole debate underscores the inherent








tery of the Munchkin.
They want the BROADEST definition when it serves their purposes and the NARROWEST definition when it does not.
The Dread Necromancer cannot be good. It's written, plain as day. Nothing about them changing alignments, it states as written in stone by God above "No Dread Necromancer can have a good alignment". Not "Dread Necromancers can have a good alignment if they put on an alignment changing item". Not some, not "special exceptions". Not "Magic makes me a rather polite and prim and generous and kind Dread Necromancer".
This is why there are no ex dread necromancers. Because there cannot BE an ex dread necromancer. If the answer to the question of "Are you a dread necromancer?" is "Yes" then you cannot have a good alignment. Even if by some bizarre chance you did get programmed amnesia (The Evil Guy wants to become a good guy in pursuit of more power so the powers of good raise him up to the absolute pinnacle of holy goodness...) the fact remains that it is
impossible to be a good dread necromancer as stated RAW.
And that's really what this debate is about. It's about munchkins who are all about interpreting certain rules in the absolute loosest fashion possible when it suits their whims and them coming down to the letter of the law when it benefits them.
Mod Note: No, now the debate is about calling people names. Folks, rule #1 is "Keep it civil." Name-calling is not civil. If you cannot keep it civil, it will be kept civil for you. ~Umbran
The game allows for paladins to turn evil, for monks to turn chaotic, for any number of alignment variations. But, as the poster above noted, unlike paladins, monks, bards, barbarians, what have you, there's nothing in RAW for ex dread necromancers. Consequently you cannot assume there can be ex dread necromancers simply because it suits your powergaming needs. It states clearly there can be no good dread necromancers. Game over.