HCLivess spoke with us in slack earlier about the 'Dapp' implementation for bismuth. They are not the traditional dapp. Ill try to remember what was explained. Perhaps he will see this and clean my description up.
The 'dapps' share timestamps, and blocks with the main chain. But they can operate individually, similar to a 'sidechain'.
As an example, you could turn any node into a casino and play games against the 'house'. The node could handle the accounting / audit side for its own clients, but still sharing blocks and timestamps with the main chain.
So player 1 plays player 2 (house) in blackjack:
player 1 bets 10 BIS on a hand, and loses.
Accounting transactions handled on the casino node:
player 1 -10 BIS
player 2 +10 BIS
I THINK this is what was being described... maybe not..