I do some editing for Wiki A, which is generally licensed in a typical wiki fashion:

Content is available under GNU FDL 1.3 unless otherwise noted.

Wiki B uses some templates I'd like to copy for reuse on Wiki A, and its general license is almost identical, except it's CC BY-SA 3.0 instead of FDL. I assume reuse of Wiki B's content on Wiki A is fine as long as the differing license is clearly stated.

The templates themselves include this wording in their documentation:

This is a chart based on [outside project] (GPLv3,
CC BY-SA 3.0) which [author] at [Wiki B] authored.

My first reading of this is that the GPL/CC-BY-SA license refers specifically and exclusively to the outside project, and does not seem to state that the templates are licensed under these terms. This leads me to believe the templates are covered by Wiki B's general license. However, the author indicates to me that these wiki templates might be GPL licensed, which is an interpretation of the templates' wording I hadn't considered, but might be valid. The author also points out that it's the code that's GPL licensed, and data content that's CC-BY-SA. The outside project itself is published on Github, but does not appear to include these templates directly.

I'm waiting on clarification of the author's stance on the exact license the templates fall under, but I think this situation warrants good answers to these questions:

  • In the general case, are user-created wiki templates usually licensed the same as the wiki content, or are they treated differently due to "not being content"? Is posting attribution (author, origin, license) on the templates' documentation enough to satisfy Wiki B's license and the "unless otherwise noted" clause in Wiki A's license?

  • In this specific case, if the templates are indeed GPLv3 licensed, does that change the requirements in any way?


This scenario is not entirely clear.

(1) Regarding the license of Wiki A, “GNU FDL 1.3 unless otherwise noted”: This seems to be an outbound license, but they may have a different inbound license, i.e. a different license under which that Wiki accepts contributions. For example, they might require all new contributions to be available under the FDL, but use that “unless otherwise noted” to account for differently licensed content in some existing pages.

(2) Regarding the licenses of the template on the CC-BY-SA 3.0-licensed Wiki B, “This is a chart based on [outside project] (GPLv3, CC BY-SA 3.0) which [author] at [Wiki B] authored”: The mention of the GPL is a red herring. There are two ways to interpret this notice

  • The templates were available under the CC-BY-SA 3.0 and could therefore be included in Wiki B, regardless of who the author is, or
  • The template author was able to contribute them to the Wiki B because they hold the copyright to these templates, regardless of the original license of the templates.

I'm assuming that the notice does refer to the templates and not specifically to an image that is shown as part of the template documentation. If the notice only refers to an image then the templates are not carrying any notices with regards to licensing so the default license of that Wiki (CC-BY-SA 3.0) would apply to the templates.

In any of the above three cases the notice as written seems to indicate that the templates are used on Wiki B under the CC-BY-SA 3.0. The notice gives no reason to believe that the templates would only be licensed under the GPL. The author's response to the contrary is highly confusing.

(3) Regarding code–data separation for templates: While this distinction is clear for most programs, templates usually copy large parts of themselves into the output and just fill in some placeholders. The output is therefore a derived work of both the template code and the data. If the output is available under the CC-BY-SA 3.0 (or the FDL), then the template and the input data need to be available under a compatible license. No version of the GPL would be a compatible license.

(4) The result is:

  • Due to the author's responses, the templates on Wiki B are licensed ambiguously and are possibly using an invalid license.
  • If the template licensing is valid, the templates are likely available under CC-BY-SA 3.0.
  • You likely cannot use these templates on the FDL-licensed Wiki because the licenses are incompatible.
  • 1
    I am [author] of [outside project], and the GPLv3 does not refer to the wiki template, but refers instead to a bunch of PHP scripts with a similar purpose that generates static pages and is not wiki-related. The wiki template code is CC-BY-SA 3.0. The template also sometimes pulls data from [outside project], and the database is also CC-BY-SA 3.0. Let me know if that clears things up (or doesn't). – posfan12 Jul 30 '18 at 23:46
  • @posfan12 Thank you for the info. This generally fits with my answer, but clarifies that the license is in fact valid. So the templates are under CC-BY-SA 3.0 and OP still cannot use them in the FDL-licensed wiki. – amon Aug 1 '18 at 10:27
  • This seems like the best answer. – posfan12 Aug 6 '18 at 6:30

You'll have to ask them. We don't know, and what is "usually done" doesn't cover this specific case.

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