Copyright and license for the add

Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
    Written by David Howells (dhowells@redhat.com)
and Copyright (C) 2016 Michael Kerrisk <mtk.man-pages@gmail.com>

License for add_key.2:

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version
2 of the License, or (at your option) any later version.