The browser icons are modified versions of the Firefox icons. Just pasting this license statement in case it is necessary:

The contents of this file are subject to the Mozilla Public License Version 1.1 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.mozilla.org/MPL/. Software distributed under the License is distributed on an “AS IS” basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for the specific language governing rights and limitations under the License. The Original Code is Mozilla 2.0.0.3. The Initial Developer of the Original Code is The Mozilla Foundation. 