The Department of Defense report on open source is called Lessons Learned but here it is in a nutshell:
Shared infrastructure makes everyone better.
Shared infrastructure is not inconsistent with the contracting mindset.
Shared infrastructure delivers both security and savings.
The report, taken in its entirety, is a very big deal, because Defense contracting is such a huge business, and because it's where closed source has taken such a dogged stand.
And that second conclusion, that open source and contracting can mix, may be the most important.
Even though it may use an open source process for developing, say, security software, doesn't mean that Secretary of Defense Gates is going over the Github for a .tar ball. He's going to continue using the same contracting process as before, choosing among competitive vendors.
But those vendors will have all shared in the fruits of an open source process, they will all be starting from the same shared store, meaning contractors will continue to have choices no matter how complex the stuff gets.