GTK+ (GIMP Toolkit) is a cross-platform widget toolkit for creating graphical user interfaces. It is one of the most popular toolkits for the X Window System, along with Qt.
GTK+ was initially created for the GNU Image Manipulation Program (GIMP), a raster graphics editor, in 1997 by Spencer Kimball and Peter Mattis, members of eXperimental Computing Facility (XCF) at University of California, Berkeley.
GTK+ is licensed under the LGPL free software license and is part of the GNU Project, which aims to create a whole free-software operating system.

ClamWin is free, open source antivirus software for Microsoft Windows. It provides a graphical user interface to the ClamAV (Clam AntiVirus) engine.

Abakt is a free backup tool with many functions that is operated via a graphical interface or the command function.
It is especially useful is the creation of groups that can each contain several backup profiles.
The tool is not capable of time-controlled data saving.

7-Zip is an open source file archiver designed originally for Microsoft Windows. 7-Zip operates with the 7z archive format, and can read and write to several other archive formats. The program can be used from a command line interface, graphical user interface, or Windows shell integration. 7-Zip began in 1999 and is actively developed by Igor Pavlov. It is related to a cross-platform port, p7zip.
7-Zip is distributed under the GNU Lesser General Public License. It was the winner of the SourceForge.net 2007 community choice awards for "Technical Design" and for "Best Project".