I can't speak to the software behind bitcoin, but the philosophy behind it seems to suggest that it couldn't have been a government agency. The space seems to be dominated by libertarian / anarchist / cyberpunk types, and many people have already stated, if bitcoins specifically & cryptocurrencies generally succeed, this will lead to an erosion of the governments' abilities to steer the economy and exert social control. So I don't think bitcoin was some governmental trojan horse released with some nefarious purpose in mind.