I have never tried DSM (hopefully one day!?) but I have used Java moss as emersed with many ways. One of my tanks is open, the moss is just climbing up from the water by on its own under not-so-hot-leds. I dont mist it or anything. One tank is glaslid on it, there the moss grows emersed pretty well on BW when the wood sucks moist from the water. The humidity in the tank is pretty high thou I mist it just once a week or two when I actually water plants growing emersed/hydro. However, the moss dried out when it grew upper parts of the tank where the wood under it dried totally, once a week misting wasn`t definetly enough. So we can think that it will survive if (just) the substrate/BW/whatever under it is wet but misting or high humidity help too. It takes some time Java moss to get adapted to an emersed life, but I think its pretty fast compered to some other mosses I have tried.
