Open-source software is computer software where the code (the rules governing its operation) is available for users to modify. This is in contrast to proprietary code, where the software vendor veils the code so users cannot view and, hence, manipulate (or steal) it. The software termed open source is not necessarily free—that is, without charge; authors can charge for its use, usually only nominal fees. According to the Free Software Foundation, “Free software” is a matter of liberty, not price. To understand the concept, you should think of “free” as in “free speech,” not as in “free food.” Free software is a matter of the users’ freedom to run, copy, distribute, study, change, and improve the software. Despite this statement, most of it is available without charge.

Open-source software is usually protected under the notion of “copyleft,” instead of “copyright” law. Copyleft does not mean releasing material to the public domain, nor does it mean near absolute prohibition from copying, like the federal copyright law. Instead, according to the Free Software Foundation, copyleft is a form of protection guaranteeing that whoever redistributes software, whether modified or not, “must pass along the freedom to further copy and share it.” Open source has evolved into a movement of sharing, cooperation, and mutual innovation, ideas that many believe are necessary in today’s cutthroat corporatization of software.