Careful. The government's right to use may not extend to cover the government's right to redistribute. And then we get into the question of whether the government must comply with copyright laws which underpin the GPL language. It's an interest thought, but I don't think you can count on it as a defense for non-governmental use until that argument has been found valid in a court of law. I'm not aware of any court precedent which would suggest that such an argument has been found valid in any other context so far.