A little off topic, regarding the brushless AC vs DC discussion.
It's the fact that we use DC power source that makes these motors DC.
If you look at the motor part only and ignore the speed controller, our brushless motors look identical to a common AC fan motor, with the only exeption of some (not all) AC motors put magnets on the inside of windings, as opposed to the outside.
The other difference is: we don't feed these outrunners with a true three phase current, our speed controllers approximate the three phases and instead of a sine wave, our speed controllers feed a "on-off" current to only two of the wires at a time. That's also why our outrunners make so much noise.
If you look at a power generator turbine closely, it's basically a three phase motor, except it's driven by steam.
Edit: To put it short, it's all in the definition.