This post introduces to free, libre or open content licenses.
The term “content” is used to refer to the combination of text, images, sound and/or artwork.
This post is part of the main post about open licenses.
Relationship between Open Content Licenses and Free and Open-Source Software (FOSS)
Open content licenses are general-purpose, and may be used on texts, graphics, music, sounds or other type of structured data.
When choosing an free and open license for software, it is NOT recommended to use an open content license, though we might find source code licensed this way.
The general recommendation for free and open-source software (FOSS) licensing is to use dedicated licenses for this purpose, as MIT, Apache 2.0 or General Public License (GPL) 2.0/3.0. You you can find a list of FOSS licences on this post.
List of Open Content Licenses
Art licenses featured on this post, sorted from less restrictive to most restrictive.
- CC0
- CC BY
- CC BY-SA
These are the ones considered open and free/libre by the Open Knowledge Foundation (OKF) and by Free Knowledge Foundation (FKF), respectively.
CC0
Creative Commons Zero, commonly abbreviated as CC0, is a public-domain-equivalent license.
The latest version for CC0 is Creative Commons Zero 1.0 Universal.
The Free Software Foundation (FSF) does not recommend to use a license for software source code that gives up patent licenses, like CC0. As explained by FSF on this external link:
[CC0] For works of software it is not recommended, as CC0 has a term expressly stating it does not grant you any patent licenses.
Because of this lack of patent grant, we encourage you to be careful about using software under this license; you should first consider whether the licensor might want to sue you for patent infringement. If the developer is refusing users patent licenses, the program is in effect a trap for users and users should avoid the program.
CC BY
CC-BY stands for Creative Commons.
It is considered a permissive license, as it allows to distribute the work or derived work under a different license, as long as you respect some restrictions like keeping the author’s name.
Latest versions is CC BY-4.0.
CC BY-SA
CC-BY-SA stands for Creative Commons Attributions-Shared Alike.
It is considered a copyleft or restrictive license, as it requires that it is distributed with the same license.
Latest version is CC BY-SA 4.0.
List of Content Licenses not considered Open
Content licenses not considered open:
- CC BY-ND
- CC BY-NC-SA
CC-BY-ND
CC-BY-ND stands for Creative Commons Attributions-No derivatives.
It is convenient for literary works (where the author agrees for distribution but refuses any alteration) or for legal texts / case law etc. that cannot be modified (even when respecting the general idea or spirit).
Latest version is CC BY-ND-2.0.
CC-BY-NC-SA
CC-BY-NC-SA stands for Creative Commons Attributions-Non commercial-Shared Alike.
Take into account that content preventing its commercial use may not be considered free and/or open by some relevant associations (like the Open Source Initiative or the Free Software Foundation) and the practice is generally discouraged by open communities.
Latest version is CC BY-NC-SA 4.0.
https://creativecommons.org/licenses/by-nc-sa/2.0/
How to mark Open Content Licenses
For CC licenses, you can use the online tool CC License Chooser that generates automatically the license text or code that should go with the content.
Marking Open Content
Open content needs to be identified as such, so the marking task needs to be done.
Ideally, the following license information should be included:
- License name
- URL to complete license (optional, but recommended)
- Author’s name (if the license type requires authorship credit)
- Work title (if applies)
- URL to the original work (optional, but recommended)
Ways to mark open content as such:
- Include a license text along the content
- Embed licensing metadata into the file
- Inform license on documentation
You can find general information about marking Creative Commons (CC) content on this external link.
For CC licenses, you can use the online tool CC License Chooser that generates automatically the license text or code that should go with the content.
Including a License Text next to the Content
You can include a text informing about the license next to the content.
Regarding Creative Commons, you can read about the right way to do it on this external link.
Embedding licensing metadata into the file
Creative Commons (CC) recommends the use of Extensible Metadata Platform (XMP) format to embed licensing metadata.
While using Creative Commons (CC) licenses, you can use the CC License Chooser to generate an XMP file that contains metadata information.
When you have an XMP file, you can import its metadata into a file by using this command:
exiftool -tagsfromfile xmp_file.xmp -all:all image_file.pngYou need to have installed Exiftool. You can read more about Exiftool on this post.
Informing License on Documentation
You can include the licensing information in the official documentation.
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External references
- Wikipedia; “Free content“; Wikipedia
- Creative Commons; “Marking“; Creative Commons
- Creative Commons; “Marking your work with a CC license“; Creative Commons