Z:gnu-www-ja-pragmatic--5eef74-That's the basic reason why th/en

That's the basic reason why the GNU General Public License is written the way it is&mdash;as a  copyleft. All code added to a GPL-covered program must be free software, even if it is put in a separate file. I make my code available for use in free software, and not for use in proprietary software, in order to encourage other people who write software to make it free as well. I figure that since proprietary software developers use copyright to stop us from sharing, we cooperators can use copyright to give other cooperators an advantage of their own: they can use our code.