Licenses: Add BSD-3-Clause W3C variant as an allowed license

Also, check if the license defined in package.json is telling us to look in the license file, instead.

package.json

@@ -157,7 +157,7 @@
 		"build:packages": "cross-env EXCLUDE_PACKAGES=babel-plugin-import-jsx-pragma,jest-console,postcss-themes node ./bin/packages/build.js",
 		"build": "npm run build:packages && cross-env NODE_ENV=production webpack",
 		"check-engines": "check-node-version --package",
-		"check-licenses": "concurrently \"wp-scripts check-licenses --prod --gpl2 --ignore=abab\" \"wp-scripts check-licenses --dev --ignore=abab\"",
+		"check-licenses": "concurrently \"wp-scripts check-licenses --prod --gpl2\" \"wp-scripts check-licenses --dev\"",
 		"ci": "concurrently \"npm run lint\" \"npm run test-unit:coverage-ci\"",
 		"predev": "npm run check-engines",
 		"dev": "npm run build:packages && concurrently \"cross-env webpack --watch\" \"npm run dev:packages\"",

packages/scripts/scripts/check-licenses.js

@@ -45,6 +45,7 @@ const gpl2CompatibleLicenses = [
 	'BSD',
 	'BSD-2-Clause',
 	'BSD-3-Clause',
+	'BSD-3-Clause-W3C',
 	'BSD-like',
 	'CC-BY-3.0',
 	'CC-BY-4.0',
@@ -111,6 +112,9 @@ const licenseFileStrings = {
 	BSD: [
 		'Redistributions in binary form must reproduce the above copyright notice,',
 	],
+	'BSD-3-Clause-W3C': [
+		'W3C 3-clause BSD License',
+	],
 	MIT: [
 		'Permission is hereby granted, free of charge,',
 		'## License\n\nMIT',
@@ -221,6 +225,11 @@ modules.forEach( ( path ) => {
 		);
 	let licenseType = typeof license === 'object' ? license.type : license;
 
+	// Check if the license we've detected is telling us to look in the license file, instead.
+	if ( licenseType && licenseFiles.find( ( licenseFile ) => licenseType.indexOf( licenseFile ) >= 0 ) ) {
+		licenseType = undefined;
+	}
+
 	/*
 	 * If we haven't been able to detect a license in the package.json file, try reading
 	 * it from the files defined in licenseFiles, instead.