Yeah, the purpose is to use whatever wild yeast is on that log to ferment you beer with.
Does kind of throw out the notion of everything having to be sanitized, when you just fire in a log you found in the woods!
Have thought about trying to collect wild yeast from around my yard, as I have some type of berry/choke cherry tree that grows wild. Thought of putting a collection device out there to see what I get. Do you do that mostly when the tree is flowering? Or does it matter.
Also thought of just picking the fruit and using them in a beer to see what it would do. I know you are supposed to sanitize/sterilize fruit like that before sticking them in, but when people are throwing logs in their fermenter they found in the woods, how much sanizatation do you really need to do?