I have never heard that the term engineer cannot be used freely. I have worked a few places where my title was software engineer even.
The terms coder, developer, engineer all mean the same to me. Maybe engineer means a higher level developer, it did where at the company when I was an "engineer". I think my current title is "sr applications developer" but I don't remember. I'd have to check my contract. Honestly I could care less what my title is, just let me architect some software and I am happy.