"Email addresses will be hidden, and won't be used for any spam / promotional actions. Emails are to verify users when comparing data with projects own data."
Have you contacted the campaign manager? If BountyDetective said that they will not make email list public, I think it was a mistake from their side. You can contact with them. It's of course not a good practise since for their mistake, the list may go to a lot of spammer.
However, I think you should use throwaway email for such purpose of activities. Why would you even use your regular email here?