Flame licker has an external flame that is drawn into the cylinder as the piston moves one way then that hot air which was drawn in cools and sucks the piston down by vacuum. Like my Chuky if you have seen that.
The Forest first draws in gas/air and then a small flame is also drawn in which ignites the gas driving the piston to the top of it's stroke and then the spent gas is exhausted on the return stroke.
The balloon is known as a gas bag, you regulate the supply to a slow steady flow which inflates the bag and then it can rapidly draw in from the bag at low pressure, bag refills during the rest of the cycle.
This is a 1:1 replica of the Forest in action on a Hydrogen based gas cocktail.