Circle использует части кода DikuMud, поэтому требует чтобы помимо лицензии Circle соблюдались еще и условия лицензии DikuMud. ROM использует куски кода DikuMud и Merc, поэтому должны соблюдаться условия лицензий ROM, DikuMud и Merc. Основная проблема DikuMud в том, что это самое настоящее проприетарное программное обеспечение, позволяющее использовать свой код только при соблюдении драконовских правил. Давайте ознакомимся с его лицензией.

/* ************************************************************************
* Copyright © 1990, 1991 *
* All Rights Reserved *
************************************************************************* */

DikuMud License
This document contains the rules by which you can use, alter or publish
parts of DikuMud. DikuMud has been created by the above five listed persons
in their spare time, at DIKU (Computer Science Instutute at Copenhagen
University). You are legally bound to follow the rules described in this
document.

Rules:

!!! DikuMud is NOT Public Domain, shareware, careware or the like!!!

You may under no circumstances make profit on *ANY* part of DikuMud in
any possible way. You may under no circumstances charge money for
distributing any part of dikumud — this includes the usual $5 charge
for «sending the disk» or «just for the disk» etc.
By breaking these rules you violate the agreement between us and the
University, and hence will be sued.

You may not remove any copyright notices from any of the documents or
sources given to you.

This license must *always* be included «as is» if you copy or give
away any part of DikuMud (which is to be done as described in this
document).

If you publish *any* part of dikumud, we as creators must appear in the
article, and the article must be clearly copyrighted subject to this
license. Before publishing you must first send us a message, by
snail-mail or e-mail, and inform us what, where and when you are
publishing (remember to include your address, name etc.)

If you wish to setup a version of DikuMud on any computer system, you
must send us a message, by snail-mail or e-mail, and inform us where
and when you are running the game. (remember to include
your address, name etc.)

Any running version of DikuMud must include our names in the login
sequence. Furthermore the «credits» command shall always cointain
our name, addresses, and a notice which states we have created DikuMud.

You are allowed to alter DikuMud, source and documentation as long as
you do not violate any of the above stated rules.

Regards,

The DikuMud Group

Note:

We hope you will enjoy DikuMud, and encourage you to send us any reports
on bugs (when you find 'it'). Remember that we are all using our spare
time to write and improve DikuMud, bugs, etc. — and changes will take their
time. We have so far put extremely many programming hours into this project.
If you make any major improvements on DikuMud we would be happy to
hear from you. As you will naturally honor the above rules, you will receive
new updates and improvements made to the game.

Лицензия DikuMud запрещает получать какую-либо финансовую выгоду при использовании его кода. Имена создателей DikuMud должны показываться в начальной сессии соединения с мадом. В маде должна быть команда «credits», которая должна показывать имена создателей DikuMud, их контакты и условия этой лицензии. Более того, содержатся требования, что если вы хотите опубликовать части кода DikuMud или запустить мад на его основе, вы должны получить на это разрешение от его авторов.

Далее, посмотрим, что написано в лицензии Merc:

Merc Release 2.1
=== Copyright and License Terms

Diku Mud is copyright © 1990, 1991 by Sebastian Hammer, Michael Seifert,
Hans Henrik St{rfeldt, Tom Madsen, and Katja Nyboe. Their license agreement
is in the file 'license.doc'.

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.

In order to use Merc you must follow the Diku license and our license. The
exact terms of the Diku license are in the file 'license.doc'. A summary of
these terms is:

— No resale or operation for profit.
— Original author's names must appear in login sequence.
— The 'credits' command must report original authors.
— You must notify the Diku creators that you are operating a Diku mud.

Our license terms are:

— Copyrights must remain in original source.
— 'Help merc' must report our help text, as shipped.

Notice that our license terms don't include keeping our names in the login
sequence. If you want to keep a line in there referring to Merc, or referring
to us by name (Furey, Hatchet, and Kahn), we'd appreciate that, but we don't
require it. But you must keep the original Diku authors in the login sequence.

If you do not follow these license terms, we will ask you to comply. If that
doesn't work, then we will talk to your system administrators (not about your
running a mud, but on the grounds that you're using our copyrighted software
without permission).

These are very generous terms for any software. If you don't want to accept
them, feel free to run some other software, or write your own.

В ней говорится, что Merc является улучшенной версией DikuMud, поэтому нужно соблюдать все условия лицензии DikuMud. Дополнительно появляются требования, чтобы в кодах мада сохранились сведения о копирайте и в маде должна быть команда «Help merc», которая должна выводить неизменную справку авторов Merc.

Теперь настала очередь лицензии Circle:

The CircleMUD License

CircleMUD is licensed software. This file contains the text of the CircleMUD license. If you wish to use the CircleMUD system in any way, or use any of its source code, you must read this license and are legally bound to comply with it.

CircleMUD is a derivative work based on the DikuMUD system written by Hans Henrik Staerfeldt, Katja Nyboe, Tom Madsen, Michael Seifert, and Sebastian Hammer. DikuMUD is also licensed software; you are legally bound to comply with the original DikuMUD license as well as the CircleMUD license if you wish to use CircleMUD.

Use of the CircleMUD code in any capacity implies that you have read, understood, and agreed to abide by the terms and conditions set down by this license and the DikuMUD license. If you use CircleMUD without complying with the license, you are breaking the law.

Using CircleMUD legally is easy. In short, the license requires three things:

1.You must not use CircleMUD to make money or be compensated in any way.
2.You must give the authors credit for their work.
3.You must comply with the DikuMUD license.

That's it — those are the main conditions set down by this license. Unfortunately, past experience has shown that many people are not willing to follow the spirit of the license, so the remainder of this document will clearly define those conditions in an attempt to prevent people from circumventing them.

The first condition says that you must not use CircleMUD to make money in any way or be otherwise compensated. CircleMUD was developed in people's uncompensated spare time and was given to you free of charge, and you must not use it to make money. CircleMUD must not in any way be used to facilitate your acceptance of fees, donations, or other compensation. Examples include, but are not limited to the following:

If you run CircleMUD, you must not require any type of fee or donation in exchange for being able to play CircleMUD. You must not solicit, offer or accept any kind of donation from your players in exchange for enhanced status in the game such as increased levels, character stats, gold, or equipment.

You must not solicit or accept money or other donations in exchange for running CircleMUD. You must not accept money or other donations from your players for purposes such as hardware upgrades for running CircleMUD.

You must not sell CircleMUD. You must not accept any type of fee in exchange for distributing or copying CircleMUD.

If you are a CircleMUD administrator, You must not accept any type of reimbursement for money spent out of pocket for running CircleMUD, i.e., for equipment expenses or fees incurred from service providers.

The second part of the license states that you must give credit to the creators of CircleMUD. A great deal of work went into the creation of CircleMUD, and it was given to you completely free of charge; claiming that you wrote the MUD yourself is a slap in the face to everyone who worked to bring you a high quality product while asking for nothing but credit for their work in return.
Specifically, the following are required:

The text in the 'credits' file distributed with CircleMUD must be preserved. You may add your own credits to the file, but the existing text must not be removed, abridged, truncated, or changed in any way. This file must be displayed when the 'credits' command is used from within the MUD.

The «CIRCLEMUD» help entry must be maintained intact and unchanged, and displayed in its entirety when the 'help circlemud' command is used.

The login sequence must contain the names of the DikuMUD and CircleMUD creators. The 'login sequence' is defined as the text seen by players between the time they connect to the MUD and when they start to play the game itself.

This license must be distributed AS IS with all copies or portions of the CircleMUD that you distribute, if any, including works derived from CircleMUD.

You must not remove, change, or modify any notices of copyright, licensing or authorship found in any CircleMUD source code files.

Claims that any of the above requirements are inapplicable to a particular MUD for reasons such as «our MUD is totally rewritten» or similar are completely invalid. If you can write a MUD completely from scratch then you are encouraged to do so by all means, but use of any part of the CircleMUD or DikuMUD source code requires that their respective licenses be followed, including the crediting requirements.

The third part of the license simply states that you must comply with the DikuMUD license. This is required because CircleMUD is a DikuMUD derivative. The DikuMUD license is included below.
You are allowed to use, modify and redistribute all CircleMUD source code and documentation as long as such use does not violate any of the rules set down by this license.

Everything below this line is the original, unmodified DikuMUD license. You must comply with the CircleMUD license above, as well as the DikuMUD license below.

Запрещается использование мада для любых коммерческих целей. Сведения об авторах Circle должны присутствовать в начальной сессии соединения с мадом. Сведения о лицензии Circle в исходных текстах мада не должны быть изменены. Справка «CIRCLEMUD» не должна быть изменена и в маде должна выводиться командой «help circlemud».

Ну, и наконец лецензия ROM:

In compiling this code, you have agreed to the following restrictions on
any operating version of ROM code:

1) following all guidelines in the diku license (contained in the file
license.doc)
2) following all guidelines in the Merc license (contained in the file
license.txt)
3) The login message to your mud must contain a notice that it is based
on ROM 2.4 beta, copyright 1993 — 1996 Russ Taylor. The help files
must include a ROM entry, readable by all players, and unaltered
from the file included with the source code, except as authorized
by the ROM authors. The login screen means the screen you see when
you first connect, excepting one-line «Do you have color?» messages,
and the readable by all players means it must be viewable by both
new and old characters on a 24-line terminal with no scrollback.
To make it more clear, you cannot put the credits on the top of
a 24-line ascii graphic, as this would cause the credits to
scroll off. In any case, final decision on compliance/non-compliance
with this requirement is left soley to the judgement of the ROM
consortium.
4) Before opening a ROM-based mud, you must send email to the author
(rtaylor@efn.org), so that I can keep track of sites for
future code releases.
5) Any use of the term Rivers of Mud remains the exclusive right of
Russ Taylor, this includes the sole right to release future versions
of ROM source code, and the title Rivers of Mud and ROM as pertains to
a mud. Names such as John's ROM, AnotherROM, and JustaROM are also
forbidden. Permission to use the name Rivers of Mud has been granted
to Zump, the current ROM implementer, his mud will remain the only one
with that privilige. As a coder, you have full rights to release your
own derivatives of the ROM code, provided they follow the restrictions of
this license, contain all appropriate README and credits files, and are
properly labelled as being derivatives of the ROM 2.4 code (just as ROM
is itself a derivative of Gamma 0.0 and Merc 2.1 code).
6) Anyone not wishing to follow terms of the ROM license shall be obligated
to delete all copies of this code in their possession. This includes, but
is not limited to, failure to display full credits for ROM, Merc, and Diku.
7) Collaboration with known Diku, Merc, or ROM license violators on any
ROM code project is strictly forbidden without written permission from
the ROM consortium (Russ Taylor, Gabrielle Taylor, and Brian Moore).
This list includes, but is not limited to, Mike Krause (Vryce),
and any other administrators involved in the mud Medievia.

(In English, this means that Alander is the only one allowed to release
ROM source code, as apposed to ROM derived source code, and that you
cannot call your mud ROM even though it uses ROM code. You also aren't
allowed to deal with code thieves)

Сведения о авторах ROM должны присутсвовать в начальной сессии соединения с мадом, причем они не должны заезжать за край экрана стандартного терминала высотой в 24 линии. В названии вашего мада не должна присутствовать абреавитура ROM. Перед тем как открывать основанный на ROM мад, вы должны связаться с автором ROM'а.