Here's what tanguy researched

I could think a little about the need for a license change on the wiki content. Here is a kind of planning to achieve that.

1. Put a banner on the wiki, linking to a page explaining the upcoming license change. That page could be used later to register the authors' agreements on the change.
2. Change the commit notice, to double-license all authored incoming changes, possibly with an option to publish them under CC-0 instead. And to license anonymous changes under CC-0, if possible.
   • simplest way to do that is to create our own licence config that links to a page explaining the double licensing
3. Contact all known contributors, asking them to re-license their work under either:
   • both the old and the new license;
   • CC-0.
4. That done, there will still be the problem of anonymous contributions. In theory, their authors only licensed them under the old license, and did not allow to re-license them. However:
   • very small changes, such as orthographical or syntactical ones may not even apply to copyright as they introduce no originality, and wil not cause any problem;
   • changes made by people that later registered would be covered by the point 3;
   • publishing something in an anonymous way to an identified project, here DokuWiki, *could* be seen as a way to give away one's copyright to the project itself; however I do not think such an argument would be acceptable to a law court, it is rather a moral one, as people could understand it;
   • the probability that someone that published changes in an anonymous way complains about the removal of the single NC clause is very low, and, if it happens, he will simply have to write to ask for removal.
   • So, my advice is not to worry, and simply count on the transition period, during which the banner will be kept on the wiki, for anonymous author to appear, and after that, considering that they agree by default.

Some comments:

• using the CC-0 by default for anonymous edits would make any future re-licensing really easier, as CC-0 allows almost anything, and that includes sub-licensing (I mean, including a CC-0 work in a whole, stating that the whole is under whatever license) or re-licensing;
• as the new license, please chose something inferior or equal to CC-BY-SA in terms of contraints (CC-BY is ok, CC-BY-NC is not), and use the version 3.0 of the CC licenses, as the 2.0 suffer from small mistakes that make them non-free to Debian (or the OSI, this is the same definition).

Hello *|FNAME|*,

You're receiving this message because you made at least
*|MMERGE3|* edits in our documentation at www.dokuwiki.org
and are therefore one of the many copyright holders.

We're currently in the process of changing the license of
our documentation from CC-BY-NC-SA to the less restrictive
CC-BY-SA.

To do this, we're asking all contributors (like you) to
agree to the license change by signing our page at

  https://www.dokuwiki.org/licensing_change

The reason for this change is that we think that the
documentation should be free in the same sense as DokuWiki
is free. This means without restrictions on commercial use.
The new license will make sure the documentation can be
distributed and used just like DokuWiki itself. More
information can be found on the page above.

Note, for simplicity of the process we have to assume, that
if you don't sign, you agree (or don't even care). However,
the more people sign, the better is the legal base of the
license change.

If you have concerns about this change, please contact us
through the mailing list or forums and we'll see how to
resolve the issues.

Kind regards,
The DokuWiki Core Team

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