"They would just use *BSD, one of the other free operating systems, or Microsoft." "I want the best software I can get in that drone....and we all know what software that is." Just some valid points/justifications for not limiting the licence. Not easy anymore it seems to make a stand and say actually not you, not they, not anyone, can use it in systems that can harm.
It isn't possible to change the license of GNU/Linux (lol), even if they wanted to. BTW, Microsoft software is used by US army too: http://www.microsoft.com/industry/government/guides/dod/default.aspx http://twitter.com/#!/microsoft_navy http://twitter.com/#!/microsoft_usaf http://twitter.com/#!/microsoft_army http://blogs.msdn.com/b/uspublicsector/ http://www.futurefed.com/
Even if it was possible to change the license to forbid its use in war, who is going to enforce this, and how? It gets even better when you try to define war. Korea was called a "police action". Using Linux would be OK there? What about cyber warfare, if anyone has actually defined what that is?