(V): Well, its down to how you define 'free.'

Wind, solar, and even hydrocarbon are all 'free' energy, in the sense that you can produce more energy from them than what you put in to extract it.

This is the same with a bird (or even a glider). You need some energy to first reach that height, but then using the energy in the thermal (potential) convert it into motion (kinetic) to theoretically stay airborne indefinitely.

However, this is not the same 'free' as being able to extract more energy than that which is available, something only a perpetual energy machine can do, i.e. create energy out of nothing, something truely free and unencumbered! However, your bird is encumbered, its height and speed is limited by the energy available in the thermal.