Sometimes Dave Winer argues that you shouldn't give your code away (or rather that he shouldn't himself) because it's part of his brain, part of him. Via an argument that the genius is in the process and not in the resulting code he now says that giving the code out would be pointless because we wouldn't understand it anyway.
So maybe he isn't so big on open source because he can't write readable code? Maybe his code is a big mess that noone else could get any use of. Or maybe showing the code would just ruin his self imposed image as some kind of coding guru.