Contributor
Part of speech: noun
Definition: A benefactor; someone who donates to charity or some cause. A person who backs, supports or champions a cause, activity or institution. A person instrumental in the creation or growth of something. A person who produces articles published in a newspaper, magazine, online publication, etc.
Subscriber
Part of speech: noun
Definition: a person who subscribes to a publication or a service
Example sentence: Being able to take a traditional cable-television subscriber and give them new widget type applications to me is huge.