If all you want to do is change that copyright line you are correct that the easiest way to do that is to simply change the contents of the BadgeOfHonor.cshtml file. It is a one line file and should be relatively easy to understand.
If someone wanted to make more extensive customizations to the footer (or other parts of the page for that matter) then Layout.cshtml is the place to look.
I assume you already know this, but for new people who may be reading this post remember the place to make the changes is not in the original Theme (TheThemeMachine or whatever) but rather in a child theme where one places a copy of the original file from
the original theme's directory.
For reference, here is the documentation on customizing themes: