Not sure it is a 100% rip off.
Kirill has actually been doing this for years but I would say he has studied Ardupilot rather closely. It would be nice to know just how similar it is under the hood. I think it inevitable that Ardupilot has become a yardstick for features and performance.
As for the GCS, they all look similar. To my mind that is the least of it. In any event you could also examine that more easily than the compiled flight controller binaries.
I think there is a degree of innovation in what he is doing. He seems to have built IMU heating into his multi layer circuit board. It looks to be a polished product.
Let's see how his plane firmware compares to Arduplane when he releases it in the next few months.
If anyone has any actual insight maybe they could post it here.