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•  License Must Not Restrict Other Software: The license must not place restrictions on other software which may be
                 distributed along with the licensed software.
              •  License Must Be Technology-Neutral: No provision of the license may be predicted on any individual technology or
                 style of interface.
              16.4.5  Types of Licenses for Free and Open-Source Software
              Some popular licenses for free software are given below:
              •  The BSD (Berkeley Software Distribution) License: They are a set of permissive free
                 software license which apply limited restrictions on the use and redistribution of the
                 software. Redistribution and use with or without modification, are allowed as per
                 three clauses in the BSD licence:
                 Clause 1:  Redistributions of source code must retain Copyright <YEAR> <COPYRIGHT HOLDER> notice, list of conditions
                         and a disclaimer.
                 Clause 2:  Redistributions in the binary form must reproduce the above copyright notice, list of conditions and the
                         following disclaimer in the documentation and/or other materials provided along with the distribution.
                 Clause 3:  Names of the copyright holder or contributors may be used to endorse or promote products derived from
                         this software without specific prior written permission.

                                     •  The MIT (Massachusetts Institute of Technology) License: This is a permissive license
                                        that has minimum restrictions on software reuse. It does not contain any clauses regarding
                                        the promotion and advertising material but does have an attribution clause, similar to the
                                        2-clause  BSD  license.  Both  the  licenses  allow  use,  redistribution,  redistribution  with
                 License                modification  for  free  or  at  a  certain  cost,  provided  it  is  accompanied  by  the  licence
                                        agreement and warranty disclaimer.  Sublicensing is an important “freedom” provided in
                                        the MIT licence as it allows adding another license that implies restrictions.


              •  The GNU General Public License (GPL):  This is a widely used license that gives end
                 users the four freedoms, namely; to run, study, share and make improvements to
                 the software.


              The distribution rights granted by the GPL for modified versions of the work are subject to certain conditions. Instead
              of putting the GNU software in the public domain, it is stated as “copyleft” Copyleft allows anyone who redistributes
              the software, with or without changes, to pass along the freedom to further copy and change it. Proprietary software
              developers use copyright to take away the users’ freedom but copyleft guarantees that every user has freedom.
              To copyleft a program, we first state that it is copyrighted; then we add distribution terms, which are a legal instrument
              that gives everyone the rights to use, modify, and redistribute the program’s code or any program derived from it but
              only if the distribution terms are unchanged. Thus, the code and the freedoms become legally inseparable. Developers
              who use the GNU GPL can copyleft a program using two steps:
              •  Provide copyright to the software
              •  Add distribution terms giving the end user legal permission to copy, distribute and/or modify it.
                 ♦  The Apache License v2: This is a permissive license that allows contributors to retain the
                   full rights to use their original contributions for any other purpose outside of Apache while
                   providing the ASF and its projects the right to distribute and build upon their work within
                   Apache pertaining to the conditions as listed below:
                   *♦Software may be freely used, reproduced, modified, distributed or sold.
                   *♦Software can be merged with other products and distributed or sold.
                   *♦Products derived or modified from licensed software can be distributed under other licenses.
                   *♦Apache software cannot be redistributed without attribution.


                482482  Touchpad Computer Science-XI
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