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:

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License.http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

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.