All software can nominally be divided into two categories – Open source Software and Closed Source Software. First are the programmes that have source text available, using which anyone can create his(her) own working version. Such software is often called “free”, one has to remember that “free” in this case does not mean “free of charge”, sometimes the source text is available only for the buyers of the programme itself and is prohibited for other users.
Availability of the source programme text gives certain freedom as for acquiring other people’s works and programme resale with slightly changed functions presented as a new product. That is why repeated tries of settling users and Open Source developers’ rights have been made. For that a number of licenses (or users’ agreements) were prepared defining conditions allowing the user of the programme to distribute and change it. Below are enumerated most popular at present variants of licensing Free Software.
BSD License (Berkly software distribution license – programme license of Berkly University) and suchlike based on it. This is the easiest variant of licensing when for changing and distributing the programme it is enough to attach the source license text and mention a list of source code authors. Providing original or changed code is not obligatory. Programmes under BSD license can be used in any other applications (commercial and free, with closed or opened code) without any limitation. An even easier variant of BSD license is MIT license. If a distributed version was altered compared to the original, then for MIT-licensed software it isn’t obligatory mentioning authors and license of the original example.
GNU GPL license (GNU General Public License)
The main task of this license is to guarantee users’ rights “to run, copy, distribute, change and improve” the source programme. One of the main requirements of GPL is the necessity of any software, developed based on or using GPL, to be also licensed by GPL.
At present most popular are the second and third editions of this license. Regardless of the fact that the third edition is in many ways more perfect than the second (some ambiguous definitions were clarified, the programme patents were explained with more details), a number of innovations in it lead to ambiguous understanding which is one of the reasons to keep this division of the software into GPLv2 and GPLv3.
Lesser General public license
This license is intended first of all for programme libraries. This license is a compromise between GPL and BSD. When licensing software under LGPL, the author thus allows using this software in applications with closed source code, but unlike BSD keeps the requirement to provide the final user with the source code of his software. As in the case of GPL there are two editions of LGPL. The second edition is an independent license included into distributed software. The third edition is an application to GPLv3, its provisions imply that licensed software fits the requirements of GPLv3 and only specify the possibility of such software usage in programmes with closed code.
