Odoo
Odoo presents an open-source point of sale user-friendly solution. It comes with a very user-friendly interface. Odoo's point of sale can be used online and offline. You can operate it on iPads, Android tablets, or laptops. It also provides the freedom of integration. You can integrate it with other Odoo's inventory and accounting applications. Through this integration, all of your point of sale transaction goes directly to inventory management and accounting. It provides you real-time figures and consolidations across all your shops without the hurdle of integrating several applications. Odoo's point of sale is more than an ordinary point of sale system. It provides your clients positive experience by improving your services. It has the ability to handle many tasks like refunds, track warranties, follow customer claims, plan order deliveries, etc.

Apache OFBiz
Apache OFBiz provides its own open-source point of the sale front-end application. This point of sale solution is a more reliable, secure, and scalable enterprise solution. It provides the freedom, to customize this solution according to your need. This framework provides all the features of pricing, promotions, facilities, and many more. It has the ability to provide order, promotion, and pricing management. It provides excellent account management like invoice, payment, billing, etc. It is released under Apache License, Version 2.0 and it is part of the Apache software foundation. Apache OFBiz is not the only point of sale application, it also included framework components and business applications for ERP, CRM, E-Business / E-Commerce, MRP, MMS/EAM.

uniCenta
uniCenta is an open-source point of sale solution. It is the branch of Openbravo point of sale and has the ability to run on displays from 800x600 upwards. It also allows you to run on multi-location and multi-terminal. It can easily manage inventory, reporting, CRM, and even employee management. It supported cross-platform like Windows XP, Windows Vista, Windows 7, WebOS, Linux, Mac OSX Java POS, ESCPos, OPOS, etc. It supported different databases like Apache Derby, MySQL, HSQLDB, PostgreSQL, Oracle databases. It also supported payment gateways, barcode scanners; weighing scales, etc. It provides the features of account management, customer information, different access levels, track inventory, transaction history, etc.