Can I create new Custom AirFrame in QGroundControl?

Is this possible to add new AirFrame in QGroundControl?
If Yes, how?
I have my own design for UAV which is not available in the list. I am using PixHawk for this UAV.

Is the QGroundControl Open Source?

The concept of an airframe is just UI which controls the FRAME parameter in ArduCopter. I you created a new frame type then I assume you update that parameter to support it as well. Just manually chnage the FRAME parameter from the parameter editor instead of using the nice ui.