I was wondering if anyone gives non-developers access to their Rails applications (like say a tech-savvy content manager or designer) and if so, how? What software? etc.
Access to what? The source code?
I assume you mean source code, css, and the like.
If they are “on” the team, sure. If they are an end-user and they “own” the application, sure. If the end-user who is owner directs that access be given to person or persons “x”, sure. All inquiries about the source code for the running app are referred to the “owner.”