This screenshot either does not contain copyright-eligible parts or visuals of copyrighted software, or the author has released it under a free license (which should be indicated beneath this notice), and as such follows the licensing guidelines for screenshots of Wikimedia Commons. You may use it freely according to its particular license. Free software license:

This work 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 3 of the License, or any later version. This work 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 version 3 of the GNU General Public License for more details. GNU General Public License v3GPLv3http://www.gnu.org/licenses/gpl-3.0.htmltrue

Note: if the screenshot shows any work that is not a direct result of the program code itself, such as a text or graphics that are not part of the program, the license for that work must be indicated separately.