From what my Dinan rep is telling me, you can only "earn" the badge if you purchased the parts directly from the Dinan Authorized Rep (usually your BMW Dealer). If you buy any Dinan parts from a fellow E46er or off Ebay, those parts will not count towards the "earned" points. In order to obtain the Legit Badge, you have to provide the purchase receipts for the parts that make up the 10 points.
I see their side of it; if they let you use parts you obtain from someone else who bought the parts, then that person has a Dinan badge but no longer qualifies (a poser?) as a Dinan car.
I picked up one of the two engine covers off a fellow E46er thinking it qualified as a point only to find out it will not. No big deal as its not really a performance item and I saved over original cost.