Z:gnu-www-ja-bsd--3439b8-The two major categories of fr/en

The two major categories of free software license are copyleft and  non-copyleft . Copyleft licenses such as the GNU GPL insist that modified versions of the program must be free software as well. Non-copyleft licenses do not insist on this. We recommend copyleft, because it protects freedom for all users, but non-copylefted software can still be free software, and useful to the free software community.