dannyvankooten/mailchimp-for-wordpress — pull request #56 by elliotlewis (2014-10-24 17:33:46+00:00)
Title: User Meta (Pro) Integration

Add a field called 'mc4wp-subscribe' to User Meta and set it's value to
'y', when checked.

Danny: Use might want to check checkbox_was_checked(), I was trying to
tie in with the parent class but I couldn't see how to map
_mc4wp_subscribe_user_meta to mc4wp-subscribe.