FoodCoop System is an Open Source group ordering and billing system. Main goal of a project is build easy to install platform for (not only Polish) food cooperatives, to help manage orders, stock, tasks and members. If you want to help us, say hello by mail: contact(at)foodcoop.pl. You can find more information on foodcoop.pl or on below documentation link.
System is based on PHP and Symfony2 framework, fcs-backend provide API to use with fcs-frontend part (which is in under development now).
Prototype version of the system was developed in 2013 members and was based on Drupal Commerce (Drupal 7) and PHP language (https://github.com/FoodCoopSystem/foodcoopsystem).
Code of project is avalible on MIT License and documentation of this system is avalible on GNU - GENERAL PUBLIC LICENSE (V2), if you contribute to that repo all your work will be avalible on same license.
Please read the docs.