Open source refers to a program or software in which the source code (the form of the program when a programmer writes a program in a particular programming language) is available to the general public for use and/or modification from its original design free of charge. The basics behind the Open Source Initiative is that when programmers can read, redistribute and modify the source code for a piece of software, the software evolves. Open source sprouted in the technological community as a response to proprietary software owned by corporations.
Proprietary software is privately owned and controlled. In the computer industry, proprietary is considered the opposite of open. A proprietary design or technique is one that is owned by a company. It also implies that the company has not divulged specifications that would allow other companies to duplicate the product.
All open source software is not distributed under the same licensing agreement. Some may use a free software license, a copyleft, or GPL compatible. The GNU GPL license is a free software license and a copyleft license, while a "GNU Lesser General Public License" is a free software license, but not a strong copyleft license. There are many different types of licenses for free software . some GNU GPL compatible, some not. You will be happy to know that PayPlans is GNU/GPL licensed open source membership selling software product.