Hm, WikiEditor and VisualEditor also mention GFDL:

So this might not be a reply tool issue – hopefully, all of these get their licenses from the same configurable source, which we maybe don’t configure on Wikidata?

Or maybe Wikidata text is supposed to be published under GFDL, and we’re just not mentioning it…?

The license messages are defined in the mediawiki/extensions/WikimediaMessages repository:

• Read mode footer: onSkinCopyrightFooter() https://phabricator.wikimedia.org/diffusion/EWME/browse/master/includes/WikimediaMessagesHooks.php$240
• Editor footer: onEditPageCopyrightWarning() https://phabricator.wikimedia.org/diffusion/EWME/browse/master/includes/WikimediaMessagesHooks.php$274
• DiscussionTools reply tool: onMessageCache__get() https://phabricator.wikimedia.org/diffusion/EWME/browse/master/includes/WikimediaMessagesHooks.php$110

At a glance, all three are different, so some of them have to be wrong. In addition to Wikidata, there are also inconsistencies with Commons and Wikinews (those projects also have different licenses than the Wikimedia default).

Based on recommendation from Legal, for text contributions on Wikidata, we can trim the last part about the the GFDL and use the following:

"By clicking "Reply", you agree to our Terms of Use and agree to irrevocably release your text under the CC BY-SA 3.0 License."

This applies to all copyright text on discussion tools on Wikidata, not just the Reply tool.

@pelberg - in the above comment, I indicated the update needed for the copyright on Wikidata. The copyright on English Wikinews also needs to be updated to drop GFDL because English Wikinews has specific exemption (to use CC BY 2.5).

So you can update this ticket to update both Wikidata and English Wikinews or create a separate ticket to update English Wikinews. Reach out if this does not make sense.