Update README.md

Changed license badge from "open source" to "GPLv3"

README.md

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 ![Image](img/banner.png?raw=true)
 
-<img src="https://img.shields.io/badge/License-Open%20Source-blue"> <img src="https://img.shields.io/badge/Device-Raspberry%20Pi%203B%2B%20%2F%204B-red"> <img src="https://img.shields.io/badge/Made%20In%20Hong%20Kong-香港開發-blueviolet">
+<img src="https://img.shields.io/badge/License-GPLv3-blue"> <img src="https://img.shields.io/badge/Device-Raspberry%20Pi%203B%2B%20%2F%204B-red"> <img src="https://img.shields.io/badge/Made%20In%20Hong%20Kong-香港開發-blueviolet">
 
 ## IMPORTANT NOTES
 The current arozos is still under intense development. System structure might change at any time. Please only develop on the current existing ArOZ Gateway Interface (AGI) JavaScript Interface or standard HTML webapps with ao_module.js endpoints.