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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.

♦ ♦A copy of the license must be redistributed along with any Apache software.
♦ ♦Up gradation or modification to the software are released under the ASF terms
To conclude, we learned about two different types of software accessible to us. The first being the public domain
software which is absolutely free without any copyright or licensing issues and secondly, the proprietary software
which has a license and the end users have to buy that license in order to use it.

538 Touchpad Computer Science (Ver. 3.0)-XI