Relicense source code from GPLv3 to GPLv3+ by adding "or later" clause to license text.

LICENSE.md

@@ -1,6 +1,8 @@
-All **source code** in `src/` is copyright © 2019 Andrew Belt and Audible Instruments contributers and is licensed under the [GNU General Public License v3.0](LICENSE-GPLv3.txt).
+All **source code** in the `src/` folder is copyright © 2017-2020 Andrew Belt and Audible Instruments contributers.
 
-The **panel graphics** in the `res/` directory are copyright © Emilie Gillet and are used and distributed with permission.
+This program is free software: you can redistribute it and/or modify it under the terms of the [GNU General Public License](https://www.gnu.org/licenses/gpl-3.0.en.html) as published by the [Free Software Foundation](https://www.fsf.org/), either version 3 of the License, or (at your option) any later version.
+
+The **panel graphics** in the `res/` folder are copyright © Emilie Gillet and are used and distributed with permission.
 
 **Dependencies** included in the binary distributable may have other licenses.
 See [LICENSE-dist.txt](LICENSE-dist.txt) for a full list.

plugin.json

@@ -1,7 +1,7 @@
 {
   "slug": "AudibleInstruments",
   "version": "1.0.2",
-  "license": "GPL-3.0-only",
+  "license": "GPL-3.0-or-later",
   "name": "Audible Instruments",
   "author": "VCV",
   "authorEmail": "contact@vcvrack.com",