JavaScript inheritance
All JavaScript files defined in the parent theme will be inherited.
Overriding inherited JavaScript: Specify a JavaScript file with the same filename in the sub-theme's .info file. For instance, to override script.js inherited from a parent theme, add the following line to your sub-theme's .info file:
scripts[] = script.js
You will also need to create the script.js file; if you simply wish to disable the imported scripts, you can create an empty file.
In fact, there are multiple ways to add JS. We don't have to add this empty example here. I propose we remove the JS folder, devs can add JS the way they like.
We probably don't explain the inheritance of STARTERKIT/js/script.js properly in STARTERKIT/README-FIRST.txt
From https://www.drupal.org/docs/7/theming/creating-a-sub-theme: