Several Lisp applications have config files that are just Lisp files run at start-up. Emacs is an example. You can (and people do) put absolutely any code in there. There's no need to restrict it to just setting variables.
So what's the difference between a config file and code? Config files aren't compiled (so no need to rebuild when you change them) and they are intended to be modified by the user, while other code isn't.
So what's the difference between a config file and code? Config files aren't compiled (so no need to rebuild when you change them) and they are intended to be modified by the user, while other code isn't.