diff --git a/includes/ApiCategoryTree.php b/includes/ApiCategoryTree.php
index 55a81238..f512ea4c 100644
--- a/includes/ApiCategoryTree.php
+++ b/includes/ApiCategoryTree.php
@@ -1,4 +1,20 @@
 <?php
+/**
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ */
 
 class ApiCategoryTree extends ApiBase {
 	public function execute() {
diff --git a/includes/CategoryTree.php b/includes/CategoryTree.php
index 5fdb117e..57359a07 100644
--- a/includes/CategoryTree.php
+++ b/includes/CategoryTree.php
@@ -1,15 +1,31 @@
 <?php
 /**
- * Core functions for the CategoryTree extension, an AJAX based gadget
- * to display the category structure of a wiki
+ * © 2006-2007 Daniel Kinzler
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
  *
  * @file
  * @ingroup Extensions
  * @author Daniel Kinzler, brightbyte.de
- * @copyright © 2006-2007 Daniel Kinzler
- * @license GPL-2.0-or-later
  */
 
+/**
+ * Core functions for the CategoryTree extension, an AJAX based gadget
+ * to display the category structure of a wiki
+ */
 class CategoryTree {
 	public $mOptions = [];
 
diff --git a/includes/CategoryTreeCategoryPage.php b/includes/CategoryTreeCategoryPage.php
index e90ed519..77ab51a0 100644
--- a/includes/CategoryTreeCategoryPage.php
+++ b/includes/CategoryTreeCategoryPage.php
@@ -1,4 +1,22 @@
 <?php
+/**
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
 
 class CategoryTreeCategoryPage extends CategoryPage {
 	public $mCategoryViewerClass = CategoryTreeCategoryViewer::class;
diff --git a/includes/CategoryTreeCategoryViewer.php b/includes/CategoryTreeCategoryViewer.php
index 3e5e0ae2..434d7222 100644
--- a/includes/CategoryTreeCategoryViewer.php
+++ b/includes/CategoryTreeCategoryViewer.php
@@ -1,4 +1,22 @@
 <?php
+/**
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
 
 class CategoryTreeCategoryViewer extends CategoryViewer {
 	public $child_cats;
diff --git a/includes/CategoryTreeHidePrefix.php b/includes/CategoryTreeHidePrefix.php
index ac25b529..29d69b70 100644
--- a/includes/CategoryTreeHidePrefix.php
+++ b/includes/CategoryTreeHidePrefix.php
@@ -1,14 +1,30 @@
 <?php
-
 /**
- * Constants for use with the hideprefix option,
- * defining when the namespace prefix should be hidden.
+ * © 2006 Daniel Kinzler
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
  *
  * @file
  * @ingroup Extensions
  * @author Daniel Kinzler, brightbyte.de
- * @copyright © 2006 Daniel Kinzler
- * @license GPL-2.0-or-later
+ */
+
+/**
+ * Constants for use with the hideprefix option,
+ * defining when the namespace prefix should be hidden.
  */
 class CategoryTreeHidePrefix {
 
diff --git a/includes/CategoryTreeHooks.php b/includes/CategoryTreeHooks.php
index c9dea564..a30d4932 100644
--- a/includes/CategoryTreeHooks.php
+++ b/includes/CategoryTreeHooks.php
@@ -1,15 +1,31 @@
 <?php
 /**
- * Hooks for the CategoryTree extension, an AJAX based gadget
- * to display the category structure of a wiki
+ * © 2006-2008 Daniel Kinzler and others
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
  *
  * @file
  * @ingroup Extensions
  * @author Daniel Kinzler, brightbyte.de
- * @copyright © 2006-2008 Daniel Kinzler and others
- * @license GPL-2.0-or-later
  */
 
+/**
+ * Hooks for the CategoryTree extension, an AJAX based gadget
+ * to display the category structure of a wiki
+ */
 class CategoryTreeHooks {
 
 	public static function shouldForceHeaders() {
diff --git a/includes/CategoryTreeMode.php b/includes/CategoryTreeMode.php
index 7a811184..48ff6133 100644
--- a/includes/CategoryTreeMode.php
+++ b/includes/CategoryTreeMode.php
@@ -1,13 +1,29 @@
 <?php
-
 /**
- * Constants for use with the mode, defining what should be shown in the tree.
+ * © 2006 Daniel Kinzler
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
  *
  * @file
  * @ingroup Extensions
  * @author Daniel Kinzler, brightbyte.de
- * @copyright © 2006 Daniel Kinzler
- * @license GPL-2.0-or-later
+ */
+
+/**
+ * Constants for use with the mode, defining what should be shown in the tree.
  */
 class CategoryTreeMode {
 
diff --git a/includes/CategoryTreePage.php b/includes/CategoryTreePage.php
index b352ed5f..202e84e8 100644
--- a/includes/CategoryTreePage.php
+++ b/includes/CategoryTreePage.php
@@ -1,15 +1,31 @@
 <?php
 /**
- * Special page for the CategoryTree extension, an AJAX based gadget
- * to display the category structure of a wiki
+ * © 2006 Daniel Kinzler
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
  *
  * @file
  * @ingroup Extensions
  * @author Daniel Kinzler, brightbyte.de
- * @copyright © 2006 Daniel Kinzler
- * @license GPL-2.0-or-later
  */
 
+/**
+ * Special page for the CategoryTree extension, an AJAX based gadget
+ * to display the category structure of a wiki
+ */
 class CategoryTreePage extends SpecialPage {
 	public $target = '';
 
diff --git a/modules/ext.categoryTree.css b/modules/ext.categoryTree.css
index 495a34f8..418a0754 100644
--- a/modules/ext.categoryTree.css
+++ b/modules/ext.categoryTree.css
@@ -1,11 +1,26 @@
 /**
  * Stylesheet for the CategoryTree extension.
  *
+ * © 2006 Daniel Kinzler
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
  * @file
  * @ingroup Extensions
  * @author Daniel Kinzler, brightbyte.de
- * @copyright © 2006 Daniel Kinzler
- * @licence GNU General Public Licence 2.0 or later
  */
 
 .client-js #mw-subcategories ul {
diff --git a/modules/ext.categoryTree.js b/modules/ext.categoryTree.js
index a3c8b12a..18a92719 100644
--- a/modules/ext.categoryTree.js
+++ b/modules/ext.categoryTree.js
@@ -1,11 +1,26 @@
 /**
  * JavaScript for the CategoryTree extension.
  *
+ * © 2006 Daniel Kinzler
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
  * @file
  * @ingroup Extensions
  * @author Daniel Kinzler, brightbyte.de
- * @copyright © 2006 Daniel Kinzler
- * @licence GNU General Public Licence 2.0 or later
  */
 
 /* eslint no-use-before-define: ["error", { "functions": false }] */