NASA Will Tinker With Open-Source Rocket for Return to Moon, Popular Mechanics
"The "brains" of the Ares I rocket that will send four astronauts back to the moon sometime in the next 12 years will be built by Boeing, NASA announced todaybut the specifications will be open-source and non-proprietary, so that other companies can bid on future contracts. The avionics unit will provide guidance, navigation and control for the launch rocket, which will carry the Orion crew vehicle into Earth orbit."
Editor's note: Given the increased labeling of all things associated with Ares 1 as being ITAR sensitive I am not certain how NASA is going to truly do this "open source" stuff.
Editor's update: According to a NASA source: "The IU/avionics and software are owned, developed, and designed by the NASA One Team. This is not open sourced. The SAS, CEI specs, etc. are all ITAR-Export controlled."