[Glice]

I think it's not a case of 'copywriting history' so much as a question of academic referencing; Brown presents the historical 'facts' (which are not facts but assertions and speculations; nonetheless, they function as putative facts) in tdvc as his own, or rather, does not credit their source. Because there is an adendum to tdvc to say which parts are Brown's own fiction and which are 'facts' (used in this putative sense) of his own discovery or investigation, it seems perfectly reasonable that if it can be shown that Brown sourced these 'facts' from the holy blood and the holy grail, he should be made culpable for copywrite infringment.

To explain: If I write a work of fiction based on Kant's Third Critique, which uses the same ideas without giving credit, then I am stealing from him. Of course, a lot of these ideas could be arrived at without my reading it; however, the case with historical documents is that they rely upon a large amount of specialised investigation in a specific field; that is, it is unlikely I would discover the same things as are common to tdvc and the holy blood and the holy grail on my own; and as one precedes the other, it seems incredibly unlikely that Brown sourced his assertions from anywhere other than the holy blood....

So I believe it's a question of academic referencing more than it is copyrighting history. Isn't it?