dar is a shell command that backs up directory trees and files. It has been tested under Linux, Windows, Solaris, FreeBSD, NetBSD, MacOS X and several other systems, it is released under the GNU General Public License (GPL). Since version 2.0.0 an Application Interface (API) is available, opening the way for external/independent Graphical User Interfaces (GUIs) like kdar. This API relies on the libdar library, which is the core part of DAR programs; as such, the API is released under the GPL. Consequently, to use the API, your program must be released under the GPL as well.