Update README with dual licensing

README.md

@@ -41,3 +41,15 @@ To release a new version of the module, you'll have to:
 1. Update the version in `compound/build.gradle.kts`. 
 2. Create a `version-x.y.z` branch and create a PR.
 3. When the PR is merged, a new tag will be created and the module will automatically be published to Maven Central.
+
+## Copyright and License
+
+Copyright (c) 2023 - 2025 New Vector Ltd
+
+This software is dual licensed by New Vector Ltd (Element). It can be used either:
+
+(1) for free under the terms of the GNU Affero General Public License (as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version); OR
+
+(2) under the terms of a paid-for Element Commercial License agreement between you and Element (the terms of which may vary depending on what you and Element have agreed to).
+
+Unless required by applicable law or agreed to in writing, software distributed under the Licenses is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the Licenses for the specific language governing permissions and limitations under the Licenses.