This is rbldnsd.

The current source tree is mantained by The Spamhaus Project Ltd.
The original source was written originally by Michael Tokarev <mjt+rbldnsd@corpit.ru>


The current source and documentation can be found at:
  https://rbldnsd.io/


The original, unmantained source and debian packages can always be found at:
  http://www.corpit.ru/mjt/rbldnsd.html


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.
