diff --git a/package.json b/package.json
index c0209e6..46c718b 100644
--- a/package.json
+++ b/package.json
@@ -29,7 +29,7 @@
 		"jest": "jest",
 		"jest:coverage": "jest --coverage",
 		"lint": "eslint . --cache --ext js,jsx --ignore-path .gitignore",
-		"lint:licenses": "license-checker --direct --onlyAllow=\"0BSD;Apache-2.0;BSD-2-Clause;BSD-3-Clause;ISC;MIT;Unlicense\" --production --summary",
+		"lint:licenses": "node scripts/license-checker.js",
 		"lint:prettier": "prettier . -w -u",
 		"lint:prettier:ci": "prettier . -c -u",
 		"prepare": "husky install",
@@ -66,7 +66,9 @@
 		"husky": "^8.0.3",
 		"jest": "^29.4.2",
 		"license-checker": "^25.0.1",
-		"prettier": "^2.8.4"
+		"prettier": "^2.8.4",
+		"spdx-copyleft": "^1.0.0",
+		"upath": "^2.0.1"
 	},
 	"dependencies": {
 		"fastify-plugin": "^4.5.0"
diff --git a/scripts/license-checker.js b/scripts/license-checker.js
new file mode 100644
index 0000000..2e36573
--- /dev/null
+++ b/scripts/license-checker.js
@@ -0,0 +1,87 @@
+/* eslint-disable security-node/detect-crlf */
+/* eslint-disable security/detect-object-injection */
+/* eslint-disable import/no-extraneous-dependencies */
+/* eslint-disable no-console */
+const checker = require("license-checker");
+const copyLeftLicenses = require("spdx-copyleft");
+const { promisify } = require("util");
+
+const init = promisify(checker.init);
+const path = require("upath");
+
+/**
+ * @author Frazer Smith
+ * @description Check licenses of all direct production dependencies to
+ * ensure they are not copyleft.
+ * @param {object} options - Options object.
+ * @param {string} [options.start="__dirname/.."] - Path to start checking from.
+ */
+async function checkLicenses(
+	options = { start: path.joinSafe(__dirname, "..") }
+) {
+	console.log("Checking licenses of direct production dependencies...");
+
+	/**
+	 * List of deprecated copyleft license identifiers
+	 *
+	 * @see https://spdx.org/licenses/
+	 */
+	const deprecatedLicenseList = [
+		"AGPL-1.0",
+		"AGPL-3.0",
+		"GFDL-1.1",
+		"GFDL-1.2",
+		"GFDL-1.3",
+		"GPL-1.0",
+		"GPL-1.0+",
+		"GPL-2.0",
+		"GPL-2.0+",
+		"GPL-2.0-with-autoconf-exception",
+		"GPL-2.0-with-bison-exception",
+		"GPL-2.0-with-classpath-exception",
+		"GPL-2.0-with-font-exception",
+		"GPL-2.0-with-GCC-exception",
+		"GPL-3.0",
+		"GPL-3.0+",
+		"GPL-3.0-with-autoconf-exception",
+		"GPL-3.0-with-GCC-exception",
+		"LGPL-2.0",
+		"LGPL-2.0+",
+		"LGPL-2.1",
+		"LGPL-2.1+",
+		"LGPL-3.0",
+		"LGPL-3.0+",
+	];
+
+	// merge copyleft licenses with deprecated licenses list
+	copyLeftLicenses.push(...deprecatedLicenseList);
+
+	const licenses = await init({
+		direct: true,
+		production: true,
+		start: options.start,
+	});
+
+	const copyLeftLicensesList = Object.keys(licenses).filter((license) =>
+		copyLeftLicenses.includes(licenses[license].licenses)
+	);
+
+	if (copyLeftLicensesList.length > 0) {
+		console.log(
+			`The following dependencies are using copyleft licenses: ${copyLeftLicensesList.join(
+				", "
+			)}`
+		);
+		process.exit(1);
+	}
+
+	console.log("No copyleft licenses found.");
+	process.exit(0);
+}
+
+// If file called directly, then run function
+if (require.main === module) {
+	checkLicenses();
+}
+
+module.exports = checkLicenses;