AffiliateWP - A powerful affiliate marketing solution for WordPress.
Girafi - Get more from your website visitors. Referrals, feedback, e-mails & more.
ReferralMagic - Turn your users and customers into referral magnets.
Ambassador - Referral Automation, Made Simple.
Echo - Golang HTTP server framework
Referral Candy - Run a fully automated, customizable and easy to integrate referral program for ecommerce.