Let me summarize the licensing situation, as I understand it, and also what needs to be done here.

• Almost all content of almost all Wikimedia projects is dual-licensed under CC BY-SA 3.0 and GFDL (according to Terms of Use § Licensing of Content). The projects migrated from GFDL to CC BY-SA 3.0 in 2009 (Licensing update), because GFDL has some annoying requirements, but despite that, new contributions are still required to be made available under GFDL.  
• There are several projects that are exceptions:
  • Wikinews projects are licensed under CC BY 2.5 only (according to configuration of wgRightsUrl).
  • Hungarian Wikinews is licensed under CC BY 3.0 only (according to the same).
  • Wikidata is licensed under CC BY-SA 3.0 only (according to configuration of wgRightsPage, and according to Stephen in Legal).  
• There are also several kinds of content that are exceptions:
  • Content of Wikidata main namespace is available under CC0 (https://www.wikidata.org/wiki/Wikidata:Copyright)
  • Content of Wikimedia Commons structured data about files is available under CC0 (I'm struggling to find a page that clearly documents this…)
  • Content of MediaWiki.org help namespace is available under CC0 (https://www.mediawiki.org/wiki/Project:PD_help)
  • Files uploaded to all wikis are available under a variety of licenses, as specified in each file's description
  • (there may be others)

The messages about licensing in each site's footer and in the editing interfaces are not the same. This is because one of them is intended for readers, while the other is for editors. The differences are:

• Messages in the editing interfaces don't even try to explain the content exceptions (I assume it's because either that content requires a special interface to edit, or because the licensing is displayed prominently elsewhere, and I assume that's okay). Messages in the site footer do try to explain them somewhat, at least on Wikidata and Commons.
• Messages in the editing interfaces state that you're releasing your edit under both CC BY-SA 3.0 and GFDL. Messages in the site footer only mention CC BY-SA 3.0 and that "additional terms may apply" (I assume that's because no reasonable reader would prefer to reuse the content under GFDL, but we must inform the editors about it).

And so, I assume that we do not want to exactly match the site footer text in the editing interfaces. We only want to make the editing interface correctly say "CC BY-SA 3.0 and GFDL", "CC BY-SA 3.0", "CC BY 2.5", or "CC BY 3.0", depending on the wiki.

So, where do we stand?

• All editing interfaces on Wikidata incorrectly state "CC BY-SA 3.0 and GFDL" instead of "CC BY-SA 3.0", including the wikitext editor, DiscussionTools, and also Flow
• DiscussionTools incorrectly states "CC BY-SA 3.0 and GFDL" on Wikinews (Flow would also be affected, but it's not deployed there)
• Everything else is correct (as far as I can tell)

Minor notes on content: on Wikidata, CC0 is not only for the main namespace (0) but also for the Property (120), Lexeme (146) and EntitySchema (640) namespaces; and on Commons, the variety of licenses applies not only to files but also to tabular data and map data in the Data namespace (486).

I've been looking into implementing this.

Although it'd be easy to just add a new localisation message for each combination of licensing and editing tool, I'm trying to solve this without doing that, because I worry that they wouldn't be translated soon, and also changing the message keys would require updates to on-wiki customizations (and it doesn't seem like a smart thing to do for the future). I want to instead pass the license names as parameters into the existing localisation messages, similar to what MobileFrontend already does.

Also, I have a few small patches for review, improving things that I found difficult to understand in the existing code: https://gerrit.wikimedia.org/r/q/topic:editing-copyright

I'm reading the code of the existing customizations, and keep finding new things that are broken…

On Wikidata and Commons, all of the mobile editors (wikitext, visual, talk page reply and talk page new topic) have empty space where the license name should be, because the code overriding the site footer text also overrides this text, incorrectly.

	Wikidata (wrong)	Commons (wrong)	Meta-Wiki (correct)
mobile wikitext	Link to a test page	Link to a test page	Link to a test page
mobile visual	Link to a test page	Link to a test page	Link to a test page
mobile talk page reply	Link to a test page	Link to a test page	Link to a test page
mobile talk page new topic	Link to a test page	Link to a test page	Link to a test page

Let's start with a small step and fix this. (I'll change the Wikidata licenses shown here to CC BY-SA only in a separate patch.)

Change 724439 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/WikimediaMessages@master] Fix missing license name in mobile editors on Wikidata and Commons

https://gerrit.wikimedia.org/r/724439

Change 725963 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/WikimediaMessages@master] Remove mention of GFDL in Wikidata editing interface copyright message

https://gerrit.wikimedia.org/r/725963

Change 725978 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/WikimediaMessages@master] Remove mention of GFDL in Wikidata mobile editors' copyright message

https://gerrit.wikimedia.org/r/725978

Change 725153 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/WikimediaMessages@master] Use explicit config for licensing/copyright message overrides

https://gerrit.wikimedia.org/r/725153

Change 726052 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[operations/mediawiki-config@master] Add explicit config for licensing/copyright message overrides

https://gerrit.wikimedia.org/r/726052

The configuration was set up in such a way that it was very impractical to test locally, and (unlike most config changes) this is messy enough that I'm not confident to get it perfect at the first try, so I'd like to change how the config works first, with the latest two patches.

As for Flow, it's affected in the same ways as DiscussionTools, but it has been undeployed from most sites (or has never been deployed), so the issues are not as apparent. Wikidata is affected though: https://www.wikidata.org/wiki/Wikidata_talk:Flow_tests?uselang=en

DiscussionTools displays incorrect licensing on all projects that do not use the standard CC BY-SA 3.0 and GFDL combo, including Wikidata (which prompted this whole task: T283231) and Wikinewses (although it has been overridden locally on some projects, e.g. English Wikinews).

Change 726052 merged by jenkins-bot:

[operations/mediawiki-config@master] Add explicit config for licensing/copyright message overrides

https://gerrit.wikimedia.org/r/726052

Mentioned in SAL (#wikimedia-operations) [2021-10-04T23:13:15Z] <urbanecm@deploy1002> Synchronized wmf-config/InitialiseSettings.php: 75645c9cc59b37dbf59942eabbc014b7dc147626: Add explicit config for licensing/copyright message overrides (T284097) (duration: 00m 59s)

I’ve looked at your changes, and they look generally okay to me, but I wouldn’t feel comfortable just merging them either. I think it would make sense to cherry-pick them all to a wmf branch, and deploy them one by one during a backport+config window (or possibly a dedicated deployment window), thoroughly testing each change on mwdebug first; and once we’re confident that it’s all correct, we can +2 the whole chain on master too. (I guess the best time to do this would be when all wikis are on the same train version, so we don’t have to backport to two branches – Monday or early Tuesday, maybe.)

I think that might be worth it for the first patch (which changes how all of the config works), but the rest of them have limited scope and are easily testable locally (you can just install the WikimediaMessages extension and change the new config setting to see the effect). We will ask QA folks to double-check all of the scenarios afterwards too (see the big table in task description).

Also I'm not done with the changes yet, here comes Flow and DiscussionTools…

Change 726654 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/DiscussionTools@master] Allow more flexible overrides for the terms-of-use messages

https://gerrit.wikimedia.org/r/726654

Change 726655 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/Flow@master] Allow more flexible overrides for the terms-of-use messages

https://gerrit.wikimedia.org/r/726655

Change 726656 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/WikimediaMessages@master] Use new hooks to override Flow and DiscussionTools messages

https://gerrit.wikimedia.org/r/726656

Change 726662 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/WikimediaMessages@master] Display correct license names in Flow and DiscussionTools

https://gerrit.wikimedia.org/r/726662

I think that fixes everything. Reviews welcome.

Change 725153 merged by jenkins-bot:

[mediawiki/extensions/WikimediaMessages@master] Use explicit config for licensing/copyright message overrides

https://gerrit.wikimedia.org/r/725153

Change 726654 merged by jenkins-bot:

[mediawiki/extensions/DiscussionTools@master] Allow more flexible overrides for the terms-of-use messages

https://gerrit.wikimedia.org/r/726654

Change 726655 merged by jenkins-bot:

[mediawiki/extensions/Flow@master] Allow more flexible overrides for the terms-of-use messages

https://gerrit.wikimedia.org/r/726655

Change 724439 merged by jenkins-bot:

[mediawiki/extensions/WikimediaMessages@master] Fix missing license name in mobile editors on Wikidata and Commons

https://gerrit.wikimedia.org/r/724439

Change 725963 merged by jenkins-bot:

[mediawiki/extensions/WikimediaMessages@master] Remove mention of GFDL in Wikidata editing interface copyright message

https://gerrit.wikimedia.org/r/725963

Change 725978 merged by jenkins-bot:

[mediawiki/extensions/WikimediaMessages@master] Remove mention of GFDL in Wikidata mobile editors' copyright message

https://gerrit.wikimedia.org/r/725978

Change 726656 merged by jenkins-bot:

[mediawiki/extensions/WikimediaMessages@master] Use new hooks to override Flow and DiscussionTools messages

https://gerrit.wikimedia.org/r/726656

Change 726662 merged by jenkins-bot:

[mediawiki/extensions/WikimediaMessages@master] Display correct license names in Flow and DiscussionTools

https://gerrit.wikimedia.org/r/726662

@EAkinloose noticed the following unexpected message on WIkidata:

Here are screenshots for the others. Feel free to flag incorrect ones.

Also, I'll be on the lookout for the fix(es) @matmarex.

	Wikidata	Commons	English Wikipedia	English Wikinews
	CC BY-SA 3.0 only + custom	CC BY-SA 3.0 and GFDL + custom	CC BY-SA 3.0 and GFDL	CC BY 2.5 only
desktop wikitext
desktop visual/NWE
mobile wikitext
mobile visual
mobile talk page reply
mobile talk page new topic
Flow
DiscussionTools

Change 737125 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/WikimediaMessages@master] Fix licensing messages on Wikidata

https://gerrit.wikimedia.org/r/737125

Change 737805 had a related patch set uploaded (by Jdlrobson; author: Jdlrobson):

[mediawiki/extensions/WikimediaMessages@master] Fix Wikidata license link in mobile editor

https://gerrit.wikimedia.org/r/737805

Change 737805 merged by jenkins-bot:

[mediawiki/extensions/WikimediaMessages@master] Fix Wikidata license link in mobile editor

https://gerrit.wikimedia.org/r/737805

Change 737125 merged by jenkins-bot:

[mediawiki/extensions/WikimediaMessages@master] Fix Flow and DiscussionTools licensing messages on Wikidata

https://gerrit.wikimedia.org/r/737125

The messages on Wikidata should be fixed by these patches (after they're deployed with the train next week).

My patch collided with work that Jon was doing on T289401, and we had to re-do a few things about how the licensing messages are defined on the mobile site. @EAkinloose Can you also re-test the "mobile" interfaces on all four wikis (in addition to testing everything on Wikidata)? Sorry… :)

Sure @matmarex. I will look into it after they've been deployed.

Thanks.

Wikinews wikitext seems to be broken on mobile. The attached image is what I currently get: Note that there is no copyright message showing up.

I have updated T284097#7486048 to reflect my new findings.

In T284097#7486048, @EAkinloose wrote:

Here are screenshots for the others. Feel free to flag incorrect ones.

Also, I'll be on the lookout for the fix(es) @matmarex.

	Wikidata	Commons	English Wikipedia	English Wikinews
	CC BY-SA 3.0 only + custom	CC BY-SA 3.0 and GFDL + custom	CC BY-SA 3.0 and GFDL	CC BY 2.5 only
desktop wikitext
desktop visual/NWE
mobile wikitext
mobile visual
mobile talk page reply
mobile talk page new topic
Flow		n/a (not used)	n/a (not deployed)	n/a (not used)
DiscussionTools

In T284097#7527827, @EAkinloose wrote:

Wikinews wikitext seems to be broken on mobile. The attached image is what I currently get: Note that there is no copyright message showing up.

I couldn't reproduce at first, then I realized that main namespace pages are correct, but in other namespaces the copyright message isn't showing up.

(main)	User

Now, note that in read mode, there's also no copyright message in the page footer in other namespaces. I didn't notice this before, but it's the same on mobile and desktop, so it seems intentional):

…and a recent change in MobileFrontend (734777 – part of the conflicting work I mentioned in T284097#7500565) has made it so that the message in the editor is partially copied from the page footer. So it's not there if the footer doesn't exist…

This only affects Wikinews and not Commons, Wikipedia etc., because on those sites we're overriding the entire copyright message to do weird things (dual-licensing on most sites, and fixing T284097#7485825 on Wikidata).

Change 742810 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/MobileFrontend@master] Display license in the editor even when not shown in read mode (e.g. creating new pages)

https://gerrit.wikimedia.org/r/742810

I actually misunderstood the cause of the problem above. It is not caused by pages being in other namespaces; it is caused by pages not existing. Jon noticed this in T111833. The rest should be correct, and this patch fixes it.

Change 742810 abandoned by Bartosz Dziewoński:

[mediawiki/extensions/MobileFrontend@master] Display license in the editor even when not shown in read mode (e.g. creating new pages)

Reason:

https://gerrit.wikimedia.org/r/742810

Change 743034 had a related patch set uploaded (by Bartosz Dziewoński; author: Bartosz Dziewoński):

[mediawiki/extensions/WikimediaMessages@master] Fix Wikinews license link in mobile editor

https://gerrit.wikimedia.org/r/743034

The MobileFrontend patch I proposed was rejected. Here's an alternative one.

Change 743034 merged by jenkins-bot:

[mediawiki/extensions/WikimediaMessages@master] Fix Wikinews license link in mobile editor

https://gerrit.wikimedia.org/r/743034

Copyright messages should now comply with local project policies. I have updated the task description to reflect this. Refer to T284097#7527837 for more info.

I checked for GrowthExperiments Structured tasks (Add link and Add image) - copyright messages are presented (the structured tasks are integrated in Editing experience, so checking it was just an extra precaution).