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+## Legal stuff
+
+The Chameleon skin is currently licensed under the GNU General Public License,
+version 3 (or any later version). Its documentation is currently licensed under
+GNU Free Documentation License, version 1.3 (or any later version). Any
+contributions must be made under these same licenses.
+
+However, it may in the future become necessary or desirable to change these
+licenses, e.g. to keep this skin legally compatible with a changed license of
+the MediaWiki software or to better position it in a changed legal context.
+
+For this reason every contributor needs to provide the following statement:
+```
+I understand and agree that the maintainer of the Chameleon skin shall have the
+irrevocable and perpetual right to make and distribute copies of any
+contribution, as well as to create and distribute collective works of any
+contribution, under the current license or under any other open source license
+chosen by the maintainer.
+```
+
+The current maintainer of the Chameleon skin is Stephan Gambke. He may appoint
+another maintainer in the future.
+
+Contributions are identified by the Git commit that introduces them.
+
+A contributor submitting a contribution as a patch to the [Wikimedia Git
+Server][wmf-git-server] using the `git review` command is unambiguously
+identified by the use of their ssh key. For this reason it is only necessary to
+provide the above statement once in the commit message of one contribution. This
+statement will then be deemed valid for all other contributions by that
+contributor.
+
+A contributor submitting a contribution using the [Gerrit Patch
+Uploader][patch-uploader] can not be unambiguously identified and thus needs to
+provide the above statement with each contribution. What's more, since it can
+not be ensured, that successive patch sets for the same patch uploaded using the
+[Gerrit Patch Uploader][patch-uploader] are indeed from the same person, this
+statement needs to be in the commit message of each and every patch set
+*starting from the very first*.
+
+### WTF!?
+
+I discussed the above text with various people. In the course of this discussion
+several questions (and answers) came up that are worth being recorded here.
+
+#### Why would you want to change the license?
+
+I do not have any specific reason in mind right now, but the above paragraph
+gives two examples for possible situations where changing the license could be
+useful: Compatibility with other software and license modernization.
+
+Some cases I can think of:
+* Right now the preferred installation method is to use Composer to install
+  Chameleon and all its dependencies. This way I can always claim, that the skin
+  is not distributed with the packages it depends on, and thus does not need to
+  take care of their licenses. However, should I want to provide a tarball with
+  the skin and all its dependencies I would have to more carefully check license
+  compatibility.
+* Chameleon itself might become part of a tarball, e.g. some pre-build,
+  pre-configured wiki for I don't know what purpose. Right now MW is GPL2
+  licensed which makes it incompatible for bundling with Chameleon at GPL3+.
+* Parts of the skin might actually be included in MW core. E.g. there is a
+  menu-building class proposed for MediaWiki, that would have a functionality
+  similar to what's contained in Chameleon. See
+  https://gerrit.wikimedia.org/r/#/c/108045/  (Ok, this is rather far-fetched,
+  but not completely impossible.)
+* If I get it right, it might be possible to use this skin (or a derivative)
+  for other frameworks. Didn't look into that, but it's conceivable.
+* I might want to include some code from elsewhere that requires a license
+  change. Although admittedly the GPL is at the more restrictive end of the
+  scale, so including software with less restrictive licenses is usually not a
+  problem. On the other hand MediaWiki on GPL2 would have for example have a
+  major problem including Apache licensed libraries.
+* Well, and finally there may be some shiny new GPL4 in the future, that
+  protects against whatever new scheme the big, bad industry has come up with.
+  For an example of such a situation see the article [Why Upgrade to
+  GPLv3][why-upgrade] by Richard Stallman.
+
+#### And what would you maybe change it to?
+
+Any open source license, that allows to maintain the Chameleon skin in a
+sensible way while still retaining as much of the spirit of the original license
+as possible. I certainly do not want to cheat contributors out of being
+recognized for their work, so while I like its radical simplicity I'd probably
+not go for [WTFPL][WTFPL].
+
+#### Don't you need to get signatures or something similar?
+
+The written signature is indeed a critical point. Many organizations (Python,
+GNU, Mozilla, Apache) actually ask for that. But I certainly do not want to
+involve myself in a lot of paperwork. So I try to get around that by asking to
+add the statement to the commit message. Sure, it is possible to change the
+history of a git repo, but doing so over all publicly available (and private)
+copies of the repo (including the ones on the WMF Git server and GitHub) should
+be not that easy.
+
+#### Isn't a MediaWiki skin (by its very nature) derivative from MediaWiki and thus infected by its license anyway?
+
+I do not think that skins and extensions are derivatives of MediaWiki. They do
+not fork and change. Instead they are pluggable libraries that may or may not be
+used with an MW installation. You could say they provide you with the means to
+create a derivative, where - if you were to actually distribute it - you would
+have to make sure all the licenses are compatible. So you might argue, that
+anybody providing a package of MediaWiki and some skins/extensions, creates a
+derivate. The MediaWiki tarball comes to mind.
+
+From a practical point of view, if skins and extensions actually were
+derivatives, it would be pointless to specify a separate license for them. And
+MediaWiki could never incorporate any library that does not have by chance the
+same license. Following that reasoning, you could even argue that all the
+software on a computer needs to be compatible with the OS license.
+
+#### Why not just wait until you come to the point where you want to change the license and ask people then?
+
+Two answers. First, it might just not be possible to get hold of all the people.
+Second, if anybody then disagrees, their contributions might have become an
+integral part of the software such that removing them would not be realistically
+feasible. And even if it were feasible it may be hard to remove their
+contributions and replace them with something having the same functionality. The
+new code will inevitably be similar to the old one and it might be hard to prove
+that the one was not derived from the other.
+
+
+[why-upgrade]: https://www.gnu.org/licenses/rms-why-gplv3.html
+[wmf-git-server]: https://git.wikimedia.org/
+[patch-uploader]: https://tools.wmflabs.org/gerrit-patch-uploader/
+[WTFPL]: http://www.wtfpl.net