add license

Author: rwieruch

README.md

@@ -28,6 +28,22 @@
   * Auth Persistence with Local Storage
   * Database with Users and Messages
 
+## License
+
+### Commercial license
+
+If you want to use this starter project to develop commercial sites, themes, projects, and applications, the Commercial license is the appropriate license. With this option, your source code is kept proprietary. Purchase an commercial license for different team sizes:
+
+* [1 Developer](https://gum.co/react-with-firebase-starter-pack-developer)
+* [Team of up to 8 Developers](https://gum.co/react-with-firebase-starter-pack-team)
+* [Unlimited Developers of an Organization](https://gum.co/react-with-firebase-starter-pack-organization)
+
+It grants you also access to the other starter projects in this GitHub organization.
+
+### Open source license
+
+If you are creating an open source application under a license compatible with the [GNU GPL license v3](https://www.gnu.org/licenses/gpl-3.0.html), you may use this starter project under the terms of the GPLv3.
+
 ## Installation
 
 * `git clone git@github.com:the-road-to-react-with-firebase/react-firebase-authentication.git`