Free, open-source and proprietary software: definitions and licenses
Free software and open-source software are terms about permissions, not simply price or the ability to see code. The definitions concern what recipients may do with a program, including using, examining, changing and redistributing it. Proprietary licensing restricts some of those activities. A license describes legal permissions and conditions; it does not, by itself, determine performance, suitability or the cost of running a system.
The Free Software Definition
Wikipedia’s account of the Free Software Definition describes four essential freedoms: running a program for any purpose, studying and changing it, redistributing copies, and distributing modified versions. Source-code access is needed for study and modification. In this terminology, free concerns freedom rather than a requirement that the software cost nothing. Paying for distribution or support does not settle whether these freedoms are present.
The Free Software Foundation publishes the definition and a list of licenses it considers to meet it. Wikipedia’s profile of the foundation identifies it as an organization supporting the free software movement. The definition and the organization are distinct from an individual project: a program's permissions come from its applicable license, not simply from an association with a movement.
Wikipedia’s history of the free software movement places the launch of the GNU Project in 1983 and the establishment of the foundation in 1985. It describes a movement concerned with securing the freedoms to run, study, modify and share software. That account explains the ethical emphasis of the term free software, while the permissions in the license remain the concrete basis for using the code.
The Open Source Definition
The Open Source Initiative’s Open Source Definition sets out ten distribution criteria and begins by distinguishing open source from mere access to source code. Its criteria include redistribution, availability of source, permission for derived works and non-discrimination against people or fields of work. They also address how rights follow redistributed software and prohibit a license from imposing its terms on unrelated software distributed alongside it.
The definition allows specified ways to protect the integrity of an author's source, such as distributing changes separately, while still permitting modified programs. It also requires technology neutrality in the license terms. These provisions concern the boundaries of permission: a license cannot qualify merely because its source can be inspected if it bars redistribution or modification in ways the definition excludes.
According to Wikipedia’s account of the Open Source Initiative, the organization was founded in February 1998 and maintains the Open Source Definition. The OSI license page states that approval follows its license review process. Approval means the license complies with that definition; it is not an assessment of a particular program's quality, support arrangements or fitness for a government task.
Copyleft and permissive families
Wikipedia’s explanation of copyleft describes the use of copyright permissions to preserve specified rights when a work is redistributed or adapted. Copyleft is therefore a licensing technique, rather than the absence of copyright. The conditions attached to sharing matter: the permission to modify a work and the obligation to preserve recipients' rights are parts of the same arrangement.
Wikipedia’s account of permissive licenses describes minimal requirements on use, modification and redistribution, often with notice and warranty terms. Such licenses can permit a derivative version to be released under proprietary terms. That differs from copyleft's preservation of specified rights in distributed derivatives. Neither family describes a software development team's skill, the availability of support, or the reliability of an application.
| License | Family | Key condition in the source |
|---|---|---|
| GNU General Public License | Copyleft | Distribution of a derivative or modification requires source for recipients under the same or equivalent terms. |
| BSD licenses | Permissive | Redistribution retains the required license notice; source distribution is not required. |
| Mozilla Public License | File-based weak copyleft | Covered source files remain under the license and available, including within a larger work. |
| Apache License | Permissive | Required notices remain; modified files identify that changes were made. |
The comparison is a distinction among conditions, rather than a ranking. The GPL article also makes clear that providing source to recipients is not a general requirement to publish every modification to the public. The MPL article describes the source file as the boundary of its conditions. Scope, distribution and the exact license text therefore matter when describing obligations.
Proprietary permission and visible source
Wikipedia’s article on proprietary software explains that proprietary programs can be either closed source or source available. Permission to inspect code is consequently different from permission to copy, change or redistribute it. A visible-source arrangement can retain restrictions that prevent it from meeting the free-software or open-source definitions. Likewise, software offered without a purchase fee can retain restrictive terms.
For an institution, the relevant comparison includes the permitted activities, redistribution conditions and compatibility with other code. The intellectual-property page explains the rights behind these terms. The publicly funded software page examines the separate question of ownership and licensing when public money pays for development, and the procurement page connects licensing to wider assessment factors.