Are the dishes/LNB the same for Dave and Dish? Can I use a dave dish for Dishnet?

As long as you are only talking about the round dishes, yes they are...you will have to use different types of multi switches though if you happen to be referring to the dtv duo dish or the dish 500...but even the dtv duo dish can be used for dish 500 by using the 110 and 119 sats...
probably a little more than you were asking...but it just came out..

Thanks