ArduPilot is an open source autopilot platform created in 2007 by the DIY Drones community that has about 600K lines of code and is supported by a wide group of developers. The main repository is mantained by Andrew Tridgell and Andy Mackray. The project keeps growing in popularity and nowadays it supports 3 kind of vehicles:
BeaglePilot is a project that aims to create an autopilot for Linux-based computers using the BeagleBone (Black) as the hardware blueprint.
The project basically concentrates in pushing forward the
AP_HAL_Linux of ardupilot.
The work performed at BeaglePilot is expected to be merged into ardupilot.