diff --git a/extensions/markdown/js/src/forum/util/apply.js b/extensions/markdown/js/src/forum/util/apply.js
index 7f206060c..d55d82c6c 100644
--- a/extensions/markdown/js/src/forum/util/apply.js
+++ b/extensions/markdown/js/src/forum/util/apply.js
@@ -1,3 +1,8 @@
+/*!
+ * Original Copyright GitHub, Inc. Licensed under the MIT License.
+ * See license text at https://github.com/github/markdown-toolbar-element/blob/master/LICENSE.
+ */
+
 import insertText from './insertText';
 import { blockStyle, isMultipleLines, multilineStyle, orderedList } from './styles';
 
diff --git a/extensions/markdown/js/src/forum/util/insertText.js b/extensions/markdown/js/src/forum/util/insertText.js
index c659a40b9..c2de8a1bd 100644
--- a/extensions/markdown/js/src/forum/util/insertText.js
+++ b/extensions/markdown/js/src/forum/util/insertText.js
@@ -1,3 +1,8 @@
+/*
+ * Original Copyright GitHub, Inc. Licensed under the MIT License.
+ * See license text at https://github.com/github/markdown-toolbar-element/blob/master/LICENSE.
+ */
+
 export let canInsertText = null;
 
 export default (textarea, { text, selectionStart, selectionEnd }) => {
diff --git a/extensions/markdown/js/src/forum/util/styles.js b/extensions/markdown/js/src/forum/util/styles.js
index 5da1dfa04..4b6715e1d 100644
--- a/extensions/markdown/js/src/forum/util/styles.js
+++ b/extensions/markdown/js/src/forum/util/styles.js
@@ -1,3 +1,8 @@
+/*
+ * Original Copyright GitHub, Inc. Licensed under the MIT License.
+ * See license text at https://github.com/github/markdown-toolbar-element/blob/master/LICENSE.
+ */
+
 export function isMultipleLines(string) {
   return string.trim().split('\n').length > 1;
 }