>Dual-use means that it could be used for civilian and military applications, not that it actually is.

This brings forward some cognitive dissonance in me. I love the open source ethics, especially the "ANYONE CAN USE THIS FOR ANY PURPOSE" tagline. But, personally, I do not want any military (especially the US military) to find any usefulness out of my projects. I'm not sure on the legal aspects of it, but if there was an SPDX-License-Identifier for GPL-3.0-NO-MILITARY (or something similar, you get the point), I'd use it on everything.