Diku Mud is copyright (C) 1990, 1991 by Sebastian Hammer, Michael Seifert, Hans Henrik Strfeldt, Tom Madsen, and Katja Nyboe. Their license agreement is in the file 'doc/license.diku.txt'.
Merc Diku Mud is a derivative of the original Diku Mud and is subject to their copyright and license agreement. Merc Diku Mud contains substantial enhancements to Diku Mud. These enhancements are copyright 1992, 1993 by Michael Chastain, Michael Quan, and Mitchell Tse. Their license agreement is in 'doc/license.merc.txt'. The license terms boil down to this: the people who wrote this mud want due credit for their work. MERC Industries had officially disolved October 13, 1993. MERC 2.2 is a compilation of various bug and typo fixes along with a few new worlds. MERC 2.2 also has a variable line pager, MOBPrograms, and player settable prompt.
SMAUG is a derivative of the version 2.1 distribution of Merc Diku Mud. SMAUG contains substantial enhancements to Merc Diku Mud, including some features of the original Diku Mud that were removed by the Merc team. Their license agreement is in 'doc/license.smaug.txt'.
SMAUG II is a derivative of the original SMAUG and is subject to their copyright and license agreement. SMAUG II contains substantial enhancements to SMAUG. These enhancements are copyright 2014 by Antonio Cao (@burzumishi) under the 'GNU GPL v2 LICENSE'.
Thanks to the SMAUG Code Team!