ME 
Open-source headless commerce platform with modular architecture for building custom storefronts, B2B workflows, and multi-region shops on Node.js
E-Commerce
Open-source shopping carts and storefront platforms.
PO 
Offline first POS and billing software for shops and restaurants, with desktop apps and a self hosted server mode for local control
PR 
Free open-source e-commerce platform with 250k+ active merchants. PHP and MySQL-based, module ecosystem, multi-language and multi-currency support out of the box
SA 
Headless open-source commerce platform with a GraphQL API, multi-channel support, and an extensible admin dashboard. Python and Django-based, self-host free