This is rbldnsd.
The current source tree is mantained by The Spamhaus Project Ltd.
The original source was written originally by Michael Tokarev <firstname.lastname@example.org>
The current source and documentation can be found at:
The original, unmantained source and debian packages can always be found at:
Copyright (C) 2016 The Spamhaus Project Ltd.
Copyright (C) 2002 Michael Tokarev
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.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.