A software license is a legal instrument which governs the usage and distribution of copyrighted software. Software licenses can fall into two broad categories:

Proprietary software licenses grant the buyer of a copy of the software the permission to use it, but ownership of the copy remains with the publisher. A limited set of rights is granted to the buyer. The buyer has to accept the terms and conditions in order to be able to use the software. Microsoft Office, for example, is distributed under a proprietary license.

Open source and free software licenses transfer ownership of the copy to the buyer/end user. The end user is free to modify the source code and redistribute the modified version(for free or at a price), with a few simple conditions that depend on the type of license. There are many open source licenses; we will look at some common ones here:

MIT License: This is probably the simplest license. It surrenders all rights that the copyright holder/publisher typically receives, including the exclusive right to commercially exploit the work. It also disclaims any express warranty and fitness for a purpose.. There is no clause prohibiting use of the names of publishing organizations and contributors for product endorsement. When the original work or “substantial portions” of it are distributed, the licensee is required to include a copyright notice and the notice giving permission to potential licensees of their rights to use the work. However, modifications may go into proprietary software and need not necessarily be redistributed.

BSD License: The BSD license is very similar to the MIT license except with respect to a major clause: the names of the contributors may not be used without their explicit permission. This provides protection to contributors in the event that the product is associated with a poorly written program.

GPL – GNU General Public License: The GPL, created by the Richard M. Stallman of the Free Software Foundation (FSF), also provides licensees with full modification and distribution rights, with two conditions: redistribution can be done under the same terms as the original license  and redistributed copies must contain the original GPL text without any modifications. This ensures that a licensee has the same rights that the licensor had over the document, the idea of copyleft. The GPL also allows value-add activities: a person can sell a guarantee that a GPL work will perform under a particular condition and make the changes necessary to achieve this goal. There are multiple versions of this license, the latest being version 3.

LGPL – GNU Lesser General Public License: This license allows work licensed under GPL to link to non-GPL software. A company could integrate LGPL software for with proprietary software for in-house use, but if the integrated work were to be sold under a proprietary license, it would violate the legal terms of the GPL. This license is generally applicable to subroutine libraries.

One of the greatest advantages of open source licensing is innovation: contrary to popular belief, programmers are willing to contribute to open source projects with only a more useful program as the reward. More people using a software and more people trying to fix known issues (in a well organized manner, as is the case with many open source software) generally results in better quality and reliability. Also, while the publisher of a proprietary software can stop supporting it after some time, it is generally quite easy to find someone on the internet who will be able to help you out with the problems you may be facing with your open source code.

Reference: http://oreilly.com/catalog/9780596005818/

Tags: BSD License, GPL, LGPL, MIT License, Open source licenses, Software licensing

This entry was posted on Wednesday, August 5th, 2009 at 10:00 am and is filed under Articles. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.