In the UK and Canadian military, there is no single overall software person, although there are technical authorities who define standards, etc, that should be used when software is developed.
FWIW, the UK Ministry of Defence actively supports the use of Commercial Off the Shelf (COTS) software. This isn't always OSS, but is at least better than building everything from scratch. A good ongoing example is the use of 'serious games' to support military training, e.g. as image generators inside simulators or as standalone desktop training packages. There are various COTS packages that fulfill both of these and other roles.
[EDIT: Typo]
By 'general purpose' I mean the baseline configuration that all non-POR (Program of Record) systems use. Ie, hardened Windows, MS Office, security monitoring, CAC authentication, and DOD certificates. There's no chance in hell that the 'general purpose' configuration will ever be changed to include OSS because it's intent is to be the 'lowest common demominator' of connected systems.
This person probably works as a grunt for the AF branch equivalent of G-6.
The COTS systems you're referring to are POR (Program of Record) systems created and supported by the product development branch. I think for the AF, it's the Air Materiel Command. They fall outside the scope of general systems support, therefore they require their own infrastructure for maintenance/support.
Source: I used to support a POR system.
The A6...?