Actually, this could be a back-door way to hamstring the US Miliary. So much software is written using open source now, if this becomes widespread you could have fringe legal groups going to court, trying to halt fielding or deployment of weapons based on this clause. The software might not even be in there--just the ACCUSATION that is is in there could be enough for some fool judge to issue a devastating ruling.
Think it can't happen? I'm sure people said the same thing about gay marriage not too long ago.