Bilfur has never encountered anything like this green slime. The only thing he can say for sure, he gets a strong intuitive sense that the slime is not hostile, aggressive, or evil. It's more of a passive hazard to the unwary, like a poisonous toadstool.
There are, indeed, rivulets of slime running up the walls. It's kind of like rain on a glass window, but in reverse, flowing up instead of down. The slime that drips down to the ground, seems to have an instinct to return to the ceiling. But it is very slow-moving; Bilfur isn't worried that it's going to chase after him, or anything like that.
OOC: Let's roll 1d6 to see how much Bilfur knows about green slime. 1d6 = 2, not much.