The default message message[1] should be good enough.

Message "Wikimedia-copyrightwarning" is provided to the cluster through Extension:WikimediaMessages[3].

It is then (manually) applied to (some!) wikis by overriding the "MediaWiki:Copyrightwarning" page on the wiki to be just {{MediaWiki:Wikimedia-copyrightwarning}}.

Aside from that being a horrible hack, hard to track (for users, developers as well as the legal department), that makes it currently impossible to use in javascript (since it would require parsing templates).

Aside from that it appears to be redundant.

If there is some legal ground that the default message in MediaWiki core does not legally suffice in obtaining permission from the user to irrevocably license it under said license, then I highly suggest the legal department considers the 10000s of wikis in the world that are not run by the Wikimedia Foundation and instead focus on fixing that message so that everybody is safe.

Either way I don't think there can be any justifiable reason for having a different message.

So under that assumption forward I look for differences other than the license agreement. And what I found was "[.., and] you agree to the Terms of use". Looks like that doesn't belong in the copyright message and is already in the footer (or should be in the footer, as it isn't related to editing).

If there is legal reasons to have to include it in the edit screen specifically, maybe we should include it in the copyright warning in core then, however I doubt that that it is legally required to refer to terms of usage from the edit page since they apply to the entire browsing experience and thusly are already referenced from the footer.

[1] https://translatewiki.net/wiki/MediaWiki:Copyrightwarning/en
[2] https://translatewiki.net/wiki/MediaWiki:Wikimedia-copyrightwarning/en
[3] https://www.mediawiki.org/wiki/Extension:WikimediaMessages

Version: wmf-deployment
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=42491