The whole PX4 project is open hardware, all hardware files are available in this public repository:
This does not conflict with the commercial use of the hardware. We are partnering with 3D Robotics to provide our hardware for the community. The project receives no payments from 3D Robotics, only prototypes of new hardware, which substantially helps the further evolvement of the project.
3D Robotics checks each board before shipping and have a known track record with the APM production. This does not apply for any third-party or self-built PX4 electronics.