The pop up message contains a Wikidata-specific copyright-notice which comes from the WikimediaMessages extension (key 'wikidata-shortcopyrightwarning').
This is hardcoded in the mw1.21-wmf10 branch in repo/incluedes/EntityView.php , which is absolutely horrible and I apologize for this.
Before the wmf11 deployment, this needs to be fixed in EntityView by calling a hook which is implemented in WikimediaMessages and which replaces the message from Wikibase as it is with the wikidata-shortcopyrightwarning message.
The hotfix for wmf10 is in here: https://gerrit.wikimedia.org/r/#/c/49694/
I surely hope it will not be backported to wmf11.
Version: unspecified
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=45645