XFce 4 is copyright © Olivier Fourdan (<fourdan@xfce.org>). The different components are copyrighted by their respective authors.
libxfce4util and xfprint are distributed under the terms of the BSD license.
xfce-mcs-manager, libxfce4mcs and libxfcegui4 are distributed under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
xfce-mcs-plugins, xfce-utils, xfce4, xfdesktop, xffm and xfwm4 are distributed 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.