One way war plays into FOSS is that enemy nations are no longer supposed to be contributing to the same projects, being from nationality XYZ is now as relevant as programming skills one has to offer, likewise open source software from specific countries might no longer be allowed.

I imagine anytime the people that control the war resources decide to use them, there are plenty of other people not interested or involved in the destruction. If the UK declares war on an African nation tomorrow, since the US is an ally you would say those other people in the US should disallow devs from the target African nation from contributing to their project?