Adjust readme, add relicense.md

Author: Salanto

README.md

@@ -75,7 +75,8 @@ The logo (`logo.png` and `logo.ico`) was designed by Lucas Carbí. The character
 
 ## Copyright
 
-The project is dual-licensed; you are free to copy, modify and distribute AO2 under the GPLv3 or the MIT license.
+The project is licensed under the GPLv3 license.
+Code that was released under the MIT/GPLv3 dual-license can be found [here](https://github.com/AttorneyOnline/AO2-Client/tree/last-dual-licensed).
 
 Copyright (c) 2016-2018 OmniTroid
 

RELICENSE.md

@@ -0,0 +1,38 @@
+# License Change Notice
+
+## What Changed
+
+This project was previously dual-licensed under both MIT and GPLv3 licenses.
+The project is now exclusively licensed under the [GPLv3](https://www.gnu.org/licenses/gpl-3.0.en.html) license.
+
+**Effective for any commit after `4db979187386326df64b9359b8de5e90468f7fc3`, tagged as `last-dual-licensed`, all new contributions and releases are licensed exclusively under GPLv3.**
+
+## Impact on Existing Forks
+
+If you forked this repository when it was available under the MIT license:
+
+### Your Existing Fork
+- **You can continue using your existing fork under the MIT license** for any code that was committed before this license change
+- The MIT license you received for that specific version remains valid and irrevocable
+- You are not required to change the license of your existing fork
+
+### Pulling New Changes
+If you pull new commits from our repository into your MIT-licensed fork:
+
+- **New code from us will be GPLv3-licensed**
+- This creates a mixed-license situation in your repository
+- Any binary built from a mixed tree must comply with GPL v3 for the whole work unless you can isolate the MIT parts as separate, independent modules
+
+### Your Options
+
+1. **Keep your current fork as-is** under MIT license and stop pulling our updates
+2. **Accept the GPLv3 license** and continue receiving updates from upstream
+3. **Fork from the last MIT commit** and maintain your own separate development
+
+## Recommendations
+
+- Review the differences between MIT and GPLv3 licenses to understand the implications
+- Consider whether GPLv3's copyleft requirements are compatible with your project goals
+
+---
+**Note**: This notice does not constitute legal advice. Please consult with qualified legal counsel for advice specific to your situation.