Yes and no. I am typically the technical lead on all the projects I work on and, with that, I bring a lot of past experience with tools and streamlined processes. A good amount of these tools tend to be open source, for obvious reasons. The military doesn't like open source, as I'm sure you've come to find out, but there are several ways around it. For instance, to use DNN, I refer to it in two lights: (1) it's a COTS product; and, (2) it's an in-house solution. These are contradictory, but I only give these answers to specific people.
I refer to DNN as a COTS product to those requiring documentation and as an in-house solution for those asking about it being approved for use on AF networks. The first response (regarding docs) allows us to not have to reverse engineer DNN just to document how it works as we would an internal project - we have very strict processes in the organization I've done my AF work for. The second response (in-house solution) can be given because we use the source version of DNN. Since we compile it in-house, that tends to blur the fact that it's open source. With this approach, we haven't had any problems with implementing DNN based on the fact that it's open source.
Most of the people that have approached us about it being open source don't really know what it means to be open source, so it's usually fairly simple to talk around them to the point that they just give up and let you go about your business. At least, that's been my experience. It changes a lot from base to base. There's another base that is very much pro open source. So much, that they implement non-approved software, knowing that they technically shouldn't. The fact is, they save money because they have experts on those products, so it's easier. They sure will suffer when those people leave, tho
Anyway, as far as open source and the military goes, you just have to learn how to play the game and talk to the right people. And, well, the fact that I have a good reputation within this organization and am fairly well known doesn't hurt any, either
That'll only last until senior management and military members cycles out, tho.