PX4 autopilot is an open source autopilot application that is meant to be an economical solution for unmanned piloted vehicles. Its software suite includes: QGroundControl, Mavlink Micro Air Vehicle Communication Protocol, 2D/3D aerial maps (Google Earth), Drag and Drop waypoints. Learn More
QGroundControl is an open source application that works with any Mavlink enabled drone. It allows you to have full control of your unmanned aerial vehicle (UAV) and planning for its flight missions. QGroundControl is compatible with Windows, Linux, OS X, iOS, and Android platforms. Its source code is available on Github. Also, it works with
MavSDK is not drone or brand specific and it is built on the Pixhawk Standard which was developed by Pixhawk Special Interest Group (orchestrated by the Dronecode Foundation). They developed it so there would be an open source library support for Mavlink based drones. You can find Readme files, code and downloads about the Pixhawk