In the article the author uses Stud as an example, the opponent has a closed draw. I would like to see an example where the draw is open (like in holdem) and see how that effects our calling/bluffing frequencies.

Are you referring to my article?

Holdem and other flop games are actually kind of different than stud and draw games, because of the fact that you both can see the river card. The math is the same, but the frequency with which your opponent will valuebet or bluff can be very different, because some river cards will make it hard for your opponent to value bet, even if he has the best hand, or might make it more likely for him to bluff.

Also, in holdem, it's much harder to make the declaration that when your opponent bets you can only beat a bluff, because it's difficult to know what he has. In the stud example, there is literally no hand he can value bet that doesn't beat us, because of the nature of our hand and our board. I suppose you can say the same in holdem if you hold a small pair or A high, your opponent would probably not valuebet a worse hand.

I was thinking that on the river you have to call less often than pot odds dictate because you already charged him to have the opportunity to bluff on the river(when a card comes that completes a draw) on the turn. When "a blank" hits on the river you should still call 100P/(P+1) % of the time when you only beat a bluff.the mathematics of poker talks about this in the chapter on multi street play.