Great news (thanks to Chris Miser from Falcon Unmanned for the tip): the US government has started requiring open source technology in its UAV purchases. See this RFP from the US Department of the Interior for example (pages 8, 10 and 12). Right now it's just the ground station software that needs to be open, but how soon until it's the whole stack?
The US Government (including the Department of Defence) already uses a lot of open source software (see this FAQ), but I think the extension of this policy to UAVs is new. Anybody know of other examples?
One other cool thing open source datapoint: DARPA awarded a half-million dollar contract to our DroneCode partners the Open Source Robotics Foundation for swarm research, including with drones!