Not one that is for Free, but one that is very complete, has great features and is affordable.
There are no free POS system for Magento, however you should consider using a paid product if your store really need POS system. And you should think about using desktop or tablet to be POS device. For example, if you are using iPad instead of desktop, you should use Magento POS ipad. If you use a PC for POS device, it is easier, as there are many POS extension for Magento.
There will be no free POS software. But this POS software is having best features as well as available at an affordable price.
If you want a POS system with advanced features and compatibility with your Magento version. Then you won’t find it for free. You can use Webkul Point of Sale(POS) module available at very reasonable price for your e-commerce business which can expand your revenue generation scope.
This module offers centralized Inventory Management for Magento online store and POS Outlet. The POS orders can be viewed in Magento Sales orders.
Even when the store is having poor or no internet connection then POS can work offline. In offline mode, all the orders, and transaction are saved locally.
Considering the convenience and benefits of a mobile application, you can also have a mobile application for your POS system - https://store.webkul.com/Magento-POS-Native-App-Builder.html
For more details, you can contact us at – firstname.lastname@example.org
IWDagency provided FREE POS System for Magento 1 in https://www.iwdagency.com/extensions/pos-system-m1.html. If you are not satisfied or are using another version, I recommend reading this article before giving the decision top 10 Magento 2 POS extension:https://www.mageplaza.com/review/pos/
I dont think there is a POS that is free but you can find a POS with reasonable price. Please find it here: https://www.connectpos.com/