Evidently, DC made a half-hearted attempt to contact him for it, and JB made just as little effort to contact them back. Here's a link to Byrne Robotics, where he answers the question directly: http://www.byrnerobotics.com/forum/forum_posts.asp?TID=52509
He's just a grumpy old man. Always was difficult to work with. They ought to lock him and Mark Waid together in a room, to work on a comic, and see who comes out alive.
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http://www.byrnerobotics.com/forum/forum_posts.asp?TID=52509