Apache OFBiz Apache OFBiz's suite of related business tools is built on a common architecture that enables organizations to customize the ERP to their needs. As a result, it's best suited for midsize or large enterprises that have the internal development resources to adapt and integrate it within their existing IT and business processes. OFBiz is a mature open source ERP system; its website says it's been a top-level Apache project for a decade. Modules are available for accounting, manufacturing, HR, inventory management, catalog management, CRM, and e-commerce. You can also try out its e-commerce web store and backend ERP applications on its demo page. Apache OFBiz's source code can be found in the project's repository. It is written in Java and licensed under an Apache 2.0 license.