The bottom of all content pages should have [[MediaWiki:Wikimedia-copyright]]. (content varies per-wiki, and per-language-setting, eg. [[mw:MediaWiki:Wikimedia-copyright/de]] vs [[mw:MediaWiki:Wikimedia-copyright]]).
The bottom of Flow pages do not currently have this message. Eg. (short page) https://www.mediawiki.org/wiki/User_talk:Jorm_%28WMF%29 If you look at its HTML, the footer-info div that contains the copyright and lastmodified is absent.
This should be added on Topic pages.
We'll add this in the right rail on Flow boards in an upcoming ticket.