GNU GPL is the most popular license for free software [Or open source]. The license is copyleft, requiring all modified and extended versions of the program to be free as well.
Often when we introduce Oscommerce eCommerce software to our customers, its no surprise that they are aware that it is free, open source.
However, some customers will have this question in mind: “If you install this software on my website, will they charge me for a cost in the next released version?”
This is where GNU GPL comes in. As you may also know, Oscommerce is released under GNU General Public License (GPL). By using GNU GPL instead of free software licenses, you are protected such that all improved versions of the software will be free.