I'd imagine the software flying the drones would have to compensate for the downdraft of the nearby drones and the turbulence. It would be interesting to see the software side of things. Can't wait for the open source project.
How it gets the positional information isn't clear. Some sources say GPS, I'm guessing that relies on the relative error being very small and not caring about the absolute error.
Similar to how WAAS works for aircraft, it's GPS plus a ground "enhancer".