WooCommerce - A freely available eCommerce plugin that enables shop facilities on your WordPress website. Functionality enabling extensions & beautiful themes available.
AffiliateWP - A powerful affiliate marketing solution for WordPress.
Thirty Bees - Open e-commerce platform designed to work out of the box.
ReferralMagic - Turn your users and customers into referral magnets.
Squarify.io - Sync inventory between Square and Shopify.
Echo - Golang HTTP server framework