Merge branch '3515871-license-fixes' into '1.0.x'

Issue #3515871 by jwilson3: Fix license discrepancies from upstream rivet-core

See merge request !24

README.md

@@ -56,3 +56,10 @@ Use the following command:
 [//]: # Do not add maintainers to cspell-project-words file
 
 * James Wilson - [jwilson3](https://www.drupal.org/u/jwilson3)
+
+## Credits
+
+This theme uses Sass variables and mixins from the
+[Rivet Design System](https://github.com/indiana-university/rivet-source)
+(BSD-3-Clause License) to compile Rivet-compatible custom CSS components,
+but does not redistribute Rivet code.

package.json

 {
   "name": "rivet",
   "version": "1.0.0",
-  "license": "BSD-3-Clause",
+  "license": "GPL-2.0+",
   "description": "An implementation of Indiana University's <a href='https://rivet.iu.edu'>Rivet Design System</a> for Drupal.",
   "author": "James Wilson <jrwilson3@gmail.com>",
   "devDependencies": {