There are several organizations in the FOSS field that publish guidelines and definitions for software licenses. Free Software Foundation maintains non-exhaustive lists of software licenses based on its definition of free software and licenses that the FSF considers non-free for a variety of reasons.  The FSF also distinguishes between free licenses of software compatible or incompatible with the FSF license of its choice, the Copyleft GNU General Public License. The Open Source Initiative defines a list of open source licenses certified according to their open source definition.  The Debian project also has a list of licenses that follow debian guidelines for free software.  Most distributed software can be categorized according to their license type (see table). The maintenance sometimes includes technical support. In this case, the degree of technical assistance, commonly known as gold, silver and bronze, may vary depending on the method of communication (. B e-mail versus telephone assistance), availability (z.B 5×8, 5 days a week, 8 hours a day) and response time (for example. B three hours). Support is also allowed per incident as an incident package (z.B five assistance incidents per year).
 A software license is a legal instrument (usually in contractual law, with or without printed material) that regulates the use or transmission of software. Under U.S. copyright, all software is copyrighted, both in source code and object code, unless the software has been developed by the U.S. government, in which case it cannot be protected by copyright.  Authors of copyrighted software may give their software to the public, in which case it is not copyrighted and therefore cannot be authorized. The question of whether public domain software and public domain licenses can be considered a kind of FOSS license has been discussed for some time. In 2004, lawyer Lawrence Rosen argued in the essay “Why the Public Domain Is Not a License” software could not really be abandoned in the public domain and therefore cannot be construed as a VERY PERMISSE license, a position that faces resistance from Daniel J. Bernstein and others.  In 2012, the dispute was finally resolved when Rosen accepted the CC0 as an open source license, while admitting that, contrary to what he had previously stated, it was possible to waive copyright, based on the decisions of the Ninth Circuit.  In the United States, Section 117 of the Copyright Act gives the holder of a specific copy of the software the explicit right to use the software with a computer, even if the use of the software with a computer requires the manufacture of occasional copies or adaptations (actions that could constitute copyright infringement).