Mention licensing and the REUSE tool in the readme

Author: Leon-hk

README.md

@@ -65,3 +65,9 @@ ln -f -s ../builder/build build
 ```
 
 Now you can make your modifications inside the builder directory and running `./build ${target}` inside the gardenlinux repo will use the local builder, rebuilding the build container if necessary.
+
+## Licensing
+
+Copyright 2025 SAP SE or an SAP affiliate company and GardenLinux contributors. Please see our [LICENSE](LICENSE) for
+copyright and license information. Detailed information including third-party components and their licensing/copyright
+information is available [via the REUSE tool](https://reuse.software).