Update README.md

Author: lgund

README.md

@@ -59,6 +59,6 @@ Pull requests are welcome. For major changes, please open an issue first to disc
 Please make sure to update tests as appropriate.
 
 ## License
-[MIT](https://choosealicense.com/licenses/mit/)
+[GPL-3.0](https://choosealicense.com/licenses/gpl-3.0/)
 
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