The Problem - OOTB dialog does now allow HTML editing
When you are using the standard Office 365 public website editor, you are stuck with the standard dialogs for header / footer / theme and such.
The "footer" dialog is woefully lacking, and doesn't even allow basic HTML editing
SharePoint Designer to the rescue ..
Yes .. I admit I didn't really expect to hear myself saying this either, but it does seem like SharePoint designer is the answer here.
The actually footer text values are stored in the SPWeb.Properties bag, in a specific property called wh_footertext.
(in fact .. if you look through the properties there are all sorts of values to play about with, including the logo URL, Footer links, site usage information, and a few HTML placeholders for things like Left Nav and the Site Map .. well worth a look!).
So, when you open up SharePoint Designer you can actually get to the Properties values by using the Site Options link in the Ribbon;
And when you edit the wh_footertext then you get complete control over the entire footer (including, interestingly enough, the wrapping SPAN tags as well!)
Having made this simple change we simply refresh our webpage and all is done :)
Another simple but quick one. Hope you find it useful!