Your dad isn't alone in using "some variation" of Norton Commander:

https://www.midnight-commander.org/ Midnight Commander: A NC clone for Linux/Unix/etc.

http://www.emacswiki.org/emacs-en/Sunrise_Commander Sunrise commander: NC clone for GNU Emacs.

And http://farmanager.com, the same for Windows. Much faster than having to use a mouse to navigate the file system. And a decent editor with syntax highlighting and plugin support included as well.

Far Manager is the only thing I miss after switching to OSX 6 years ago. Tried Midnight Commander and other alternatives, but not nearly as good imo. File search is the killer feature, so much better than any other alternative.

It runs fine under Wine on Ubuntu; maybe that's an option on OS X, too.