The GPL is not a problem. It does not always require changes to be released
Jack, your comment about the GPL - "the DOD???s use of open source code will alter the GPL for said code" - is completely off base.
The GPL does not require you to release source code for your changes, unless you give your changed code to someone else. As long as the DoD uses its changed code only within its own systems (drones, etc) for its own use, it incurs no obligations whatsoever under the GPL.
If it sold drones containing modified code to another country, then it would have to give the source code to that country. But (1) it has announced no plans to do that, (2) any buyer would insist on source code anyway to be sure that the drones it bought were really under its control.