So, what attributes does an aircraft require in order to deserve to be called a drone?
Is it the degree of remoteness of control? E.g., ability to be operated reliably beyond the visual range of its operator? Or the ability to operate autonomously or semi-autonomously?
Well, as an aerospace engineer, I don't think any vehicle should be called a drone. Unmanned [Combat] Aerial Vehicle is a better term, or even Remotely Piloted Vehicle.
But if we must use the label, let's say that a 'drone' meets one of the following:
* Has weapons
* Operates autonomously
* Operates over the horizon
* Requires runway facilities -- large remotely-piloted aircraft
Everything else is just RC, including the quadrotors in the article.
That is all.