I work in GSA as well, and I have a lot of trouble getting software approved that you use all the time, even getting nginx approved took a long time. Forget about vagrant, virtual box, recent versions of python, etc... How were you able to get ATOs to operate most of your systems and work through these policies?
(I know very little about this world) why do you need approvals to use open source software? Certainly the purse strings are tightly held, but why is use of free software restricted?
Any software used on government systems has to go through an accreditation process. This is to prevent you from pulling in some random code that may have security vulnerabilities or backdoors. Just because it is open source doesn't mean it is secure.
As an example, we've had to run security scans on jquery for god's sake and justify every occurence of random number generation to make sure it wasn't used for anything security related....
There are other things like warranty, support, size of the community, etc...
Overall, GSA is one of the best agencies when it comes to open source. It has definitely come a long way, but still a long way to go.