A Referral Bounty app is an app that is connected to Referrals.com and Contrib.com marketplace. It allows you to put a cash bounty for anyone in Contrib or Referrals.com who could send you the person you are looking for and then pay the bounty via Paypal.com.
You could also manage and see people from both networks (Contrib and Referrals.com) and their referrals.
It is available in your Apps Marketplace under your Domain Dashboard. Check the screenshot below.