The DDG was not included in the Big Book of Busts (1995), maybe because it is played so seldom. Had the DDG been included, it surely would have been attached with a skull, meaning: If you play this poison line, you deserve to lose. All the books that mention 3. c4 in the French Defence settle it simply: "An unsound pawn offer."
Unorthodox Chess Openings (1998) By Eric Schiller dedicated almost two pages for the DDG, attempting to give the definitive bust -- but failed.
The known theory is based on this line given by Paul Keres in his book Spanisch bis Französisch (1974):
1. e4 e6 2. d4 d5 3. c4 dxe4 4. Nc3 Nf6 5. f3 c5 6. d5 exd5 7. cxd5 exf3 8. Nxf3
8... Bd6, and Black
has good position with a healthy pawn.
9. Bd3 looked strong to me, though, but according to John Watson, Black is simply better after 9... O-O!.
Play the French (1996) by Watson gives a knock-out 5. Bg5 Be7 6. f3 (6. Nge2 c5 =/+) Nc6! 7. d5 exd5 8. Bxf6 Bxf6 9. cxd5 Nd4 10. Nxe4 O-O -/+.
Watson concluded an e-mail message he sent me: "What kind of opening is it where White not only doesn't have some advantage after 8 moves, but can't even get equality? There are many better gambits to play."
When an opening is officially busted, it only means that master level players can quite easily refute it. So what, most of us hardly ever play against them.
The DDG looks like busted. But why should I play something else when I have scored more than 80 % so far. If you think I am only hoaxing, challenge me for an e-mail game.
But is the DDG busted once and for all? I say: Some variations are dead, long live the DDG!