Gyro-Steve,
also, I am not quite sure what leads me to believe that it is not a flight around the world, rather than flying in many places around the world.
Well, they do have a profile on facebook
Weltflug.tv | Facebook and it really seems they did fly from Germany to Australia so far.
Unfortunately, they don't publish the more interesting details of the trip such as the length and duration of each leg or how they got they managed to get the fuel at each stop.
What I find funny is the fact that many times they do these flights for a purpose, charity or a very honorable goal instead of simply admitting to do it for the pure joy of flying.