GoodNews Subscribers are basically MODX users extended with the necessary meta informations to handle subscriptions and other mailing related stuff. The Subscribers grid lists all users from the MODx user table whether or not the have subscriptions enabled.
Users with a greyed out email address don't have GoodNews meta informations assigned or currently no subscriptions enabled. New subscribers are created through user subscriptions, manually through MODX user management or by importing.
(Screenshot: GoodNews Management Interface - Subscribers tab)
(Screenshot: GoodNews Management Interface - Edit Subscriber - Contextmenu)
(Screenshot: GoodNews Management Interface - Edit Subscriber)