"sporulating?

That's a word? LOL. I wouldn't put wild moss in your terr ... too much chance of introducing unwanted lifeforms IMO. You could, however, take the moss once the sporangia are ripe and, holding the moss over the media, gently tap the sporangia to cause the spores to be scattered in the terr. Whether the spores germinate and survive is another story. In one of my tanks, the media is always wet and humidity is about 100%. That tank does have moss growing in it, though I get periodic die-offs.