You would need to put the widget in the Categories Siderbar section. If you don't have this section, your theme needs to be updated. see here for needed changes.
Global footer widget appearing before footers of other pages.
Since updating to nodebb 1.6.1. We noticed our copyright and disclaimer widgets started appearing above footers of other page templates. e.g topic.tpl
Here is an example from source code of http://chatrooms.talkwithstranger.com/topic/6576/just-looking-for-someone-to-talk-to
PS. I know you can see the copyright message below everything on the page itself. But that's done in JS (after page load)