Relicense from GPLv3 to GPLv3+.

LICENSE.md

@@ -1,4 +1,6 @@
-All **source code** is copyright © 2019 Andrew Belt and VCV Prototype contributers and is licensed under the [GNU General Public License v3.0](LICENSE-GPLv3.txt).
+All **source code** is copyright © 2019-2020 Andrew Belt and VCV Prototype contributors.
+
+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.
 
 All **example scripts** in the `examples` directory are licensed under [CC0-1.0](https://creativecommons.org/publicdomain/zero/1.0/legalcode) (public domain).
 

plugin.json

@@ -2,7 +2,7 @@
   "slug": "VCV-Prototype",
   "name": "Prototype",
   "version": "1.2.0",
-  "license": "GPL-3.0-only",
+  "license": "GPL-3.0-or-later",
   "brand": "VCV",
   "author": "VCV",
   "authorEmail": "contact@vcvrack.com",