I second the use of CC-BY. It offers the broadest range of compatibility with the different types of open content licenses used for RPGs.
Some Creative Commons licences have the advantages of being compatible with the ORC licence.
D&D 5e is licenced under the Creative Commons Attribution 4.0 International License available at
https://creativecommons.org/licenses/by/4.0/legalcode.
The main difference between that license and the Sharealike licence (CC-BY-SA) is that it isn't viral. CC-BY-CA contains one additional clause, which is:
"If you remix, transform, or build upon the material, you must distribute your contributions under the
same license as the original."
This effectively prevents you from mixing CC-BY-SA content with ORC or OGL content. This is permitted under the
CC-BY licence.
EN Publishing gives the following neat explanation of the different Creative Commons licences:
The six CC license types are:
CC-BY (credit required)
CC BY-SA (credit required, adaptions must use the same license)
CC BY-NC (credit required, non-commercial use only)
CC BY-NC-SA (credit required, non-commercial use only, adaptions must use the same license)
CC BY-ND (credit required, no derivatives or adaptions)
CC BY-NC-ND (credit required, no derivatives or adaptions, non-commercial use only)
The advantage of the various Creative Commons licences is that they are well-supported, well-tested in court both, and widely known throughout the industry.
They are also simple to implement. All Mongoose would need to do is produce an attribution statement like the one below for EN Publishing's Advanced 5e SRD. It might also be advisable to list the specific publications covered by the licence to avoid complications with works such as Deus Vult and Sheoloth.
Here are a couple of sample attribution notices used by other RPGs:
You may use the content in the A5ESRD in any manner permitted by the license as long as you include the following attribution in your own work:
This work includes material taken from the A5E System Reference Document (A5ESRD) by EN Publishing and available at A5ESRD.com, based on
Level Up: Advanced 5th Edition, available at
www.levelup5e.com. The A5ESRD is licensed under the Creative Commons Attribution 4.0 International License available at
https://creativecommons.org/licenses/by/4.0/legalcode.
The System Reference Document 5.1 is provided to you free of charge under the terms of the Creative CommonsAttribution 4.0 International License (“CC-BY-4.0”). You are free to use this content in any manner permitted bythat license as long as you include the following attribution statement in your own work:
This work includes material taken from the System Reference Document 5.1 (“SRD 5.1”) by Wizards ofthe Coast LLC and available at
https://dnd.wizards.com/resources/systems-reference-document. TheSRD 5.1 is licensed under the Creative Commons Attribution 4.0 International License available at
https://creativecommons.org/licenses/by/4.0/legalcode.
Please do not include any other attribution regarding Wizards other than that provided above. You may, however,include a statement on your work that it is “compatible with fifth edition” or “5E compatible.”
Section 5 of CC-BY-4.0 includes a Disclaimer of Warranties and Limitation of Liability that limits our liability to you.
- The text of Ars Magica 5th Edition and its sourcebooks has been released under an open license: the Creative Commons Attribution-ShareAlike 4.0 International license (CC BY-SA 4.0).
- The Licensed Material is the TEXT of the game books. It does not include the the trade dress, artwork, cartography, or logos.
- We have created a new Ars Magica Open License logo, to let fans identify their work as open license material for Ars Magica. You are permitted but not required to use this logo.
- The open license is a COPYRIGHT license, not a TRADEMARK license; use of trademarks associated with Ars Magica may be permitted subject to conditions below.
- There is no System Reference Document (SRD). The full text of the released books may be extracted from PDFs available for sale on our webstore in most cases. In some cases, we don't have digital text and so aren't able to provide it, as in the case of text from the oldest books that may be licensed. We'll note this situation in our releases list here, if it applies.
- Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests Atlas Games endorses you or your use. Since adapted works are likely to make use of elements from numerous titles, you may use this general attribution statement:
- "Based on the material for Ars Magica, ©1993–2024, licensed by Trident, Inc. d/b/a Atlas Games®, under Creative Commons Attribution-ShareAlike 4.0 International license 4.0 ("CC-BY-SA 4.0")"
- Atlas Games trademarks — You may apply the Ars Magica Open License Logo to, and use the trademarks "Ars Magica" and "Mythic Europe" within, any Adapted Material that you produce from the Ars Magica text under the Creative Commons license. If you do so, you must add this statement in your legalese: "Ars Magica Open License Logo ©2024 Trident, Inc. The Ars Magica Open License Logo, Ars Magica, and Mythic Europe are trademarks of Trident, Inc., and are used with permission."
