Well many BDs come from the same master as their DVD counterparts but that doesn't mean they are the same thing - the resolution is the main difference between the two formats after all.

Like it or not, the policy is that if you want to download an HD restoration, you have to own the BDs and it makes sense because since the added resolution is the main value added for the BDs, acquiring the film in higher than DVD resolution some other way without also buying the official HD release is piracy.