Copyright is automatic for any written work (including programs). Often one explicitly names the copyright holder in a statement such as (c) 2013 John Doe All rights reserved. As a general rule, for works created after January 1, 1978, copyright protection lasts for the life of the author plus an additional 70 years. ------------------------------- Public Domain - works in the public domain can be used by anyone for any purpose. The author does not retain any control. There must be an explicit statement that the work is in the public domain in order to ovverride the default copyright. ------------------------------ copyleft FSF(GNU) - Richard Stallman GNU General Public License (GPL) version 3 This is the latest version of the GNU GPL: a free software license, and a copyleft license. We recommend it for most software packages. The GPL The GPL, or General Public License, was developed by Richard M. Stallman (rms) for his GNU project, which aims to replace all proprietary software with free (“as in speech, not as in beer,” as Stallman says) software. The license, which is on its third version, is famous for its “copylefting.” Under the copyleft scheme, if you make changes to GPL code, the modified code is also under the GPL. That means that you must make the source code available to anyone else who takes the code and if they make changes, they must do the same in turn. The GPL might be the most popular free/open source license available today, used in many projects, including the Linux kernel(though it still uses version 2). ---------------------------------- GNU Lesser General Public License (LGPL) version 3 This is the latest version of the LGPL: a free software license, but not a strong copyleft license, because it permits linking with non-free modules. It is compatible with GPLv3. We recommend it for special circumstances only. The LGPL places copyleft restrictions on the program governed under it but does not apply these restrictions to other software that merely link with the program. There are, however, certain other restrictions on this software.[further explanation needed] The LGPL is primarily used for software libraries, although it is also used by some stand-alone applications. --------------------------------------- Modified BSD license This is the original BSD license, modified by removal of the advertising clause. It is a simple, permissive non-copyleft free software license, compatible with the GNU GPL. The BSD license comes from Unix variant Berkeley Software Distribution developed by some brilliant programmers in the ‘80s and ‘90s. The modern 2-clause version (made famous by the FreeBSD project) is short enough to be reproduced verbatim: Copyright (c) , All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. Previous versions required that advertisements of products using the software credit the organizations. This became known as the infamous “advertising clause,” and could become unwieldy for products that incorporated more than one BSD-licensed software project. It was also incompatible with the GPL, which is mentioned below. The BSD license allows developers to incorporate code in a product and still release proprietary software, without having to relicense the whole thing as open source. ==================== Creative Commons The original set of licenses all grant the "baseline rights", such as the right to distribute the copyrighted work worldwide, without changes, at no charge.[2] The details of each of these licenses depends on the version, and comprises a selection of four conditions: Attribution Attribution (by) Licensees may copy, distribute, display and perform the work and make derivative works based on it only if they give the author or licensor the credits in the manner specified by these. Non-commercial Noncommercial (nc) Licensees may copy, distribute, display, and perform the work and make derivative works based on it only for noncommercial purposes. Non-derivative No Derivative Works (nd) Licensees may copy, distribute, display and perform only verbatim copies of the work, not derivative works based on it. Share-alike Share-alike (sa) Licensees may distribute derivative works only under a license identical to the license that governs the original work. (See also copyleft.) Combinations Mixing and matching these conditions produces sixteen possible combinations, of which eleven are valid Creative Commons licenses and five are not. Of the five invalid combinations, four include both the "nd" and "sa" clauses, which are mutually exclusive; and one includes none of the clauses. Of the eleven valid combinations, the five that lack the "by" clause have been retired because 98% of licensors requested attribution, though they do remain available for reference on the website.[3][4][5] This leaves six regularly used licenses: Attribution alone (by) – CC-by icon Attribution + NoDerivatives (by-nd) – CC-by-ND icon Attribution + ShareAlike (by-sa) – CC-by-SA icon Attribution + Noncommercial (by-nc) – CC-by-NC icon Attribution + Noncommercial + NoDerivatives (by-nc-nd) – CC-by-NC-ND icon Attribution + Noncommercial + ShareAlike (by-nc-sa) – CC-by-NC-SA icon For example, the Creative Commons Attribution (BY) license allows one to share and remix (create derivative works), even for commercial use, so long as attribution is given.[6]