A person who produces articles published in a newspaper, magazine, online publication, etc.
A benefactor; someone who donates to charity or some cause.
A person (or thing) instrumental in the creation or growth of something.
A person who backs, supports or champions a cause, activity or institution.
A professional writer who is paid to write material that is officially credited to another person; one who writes on behalf of someone else, often for a celebrity.
Smith was listed as the author of his autobiography, but a ghostwriter did most of the work.