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The Open Source Initiative (OSI) defines open-source software by the rights its license gives recipients—not simply by whether its code can be read. Under the Open Source Definition (OSD), a qualifying license must satisfy ten criteria, including rights to redistribute and modify the software without discrimination against people or fields of work.
What does the Open Source Definition mean?
The OSD is a set of conditions for software distribution. It describes the freedoms a license must preserve so recipients can access, use, modify, and share software, whether modified or unmodified. Publishing source code is necessary under the definition, but visibility alone does not make software open source. The Open Source Definition sets out the ten criteria.
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OSI describes itself as the steward of the definition, saying, “As steward of the Open Source Definition, we set the foundation for the open source software ecosystem.”
What are the OSD’s ten criteria?
These are requirements for the license governing distribution, not a project checklist about how its code is hosted or displayed.
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- Free redistribution: The license must not restrict a party from selling or giving away the software as part of a larger software distribution.
- Source code: The software must include source code or make it available in a form that allows modification.
- Derived works: The license must allow modifications and derived works, and their distribution under the same terms as the original software.
- Integrity of the author’s source code: A license may require modified versions to use a different name or version number, or to distribute patches separately, but must allow distribution of software built from modified source.
- No discrimination against persons or groups: The license cannot exclude people or groups from exercising its rights.
- No discrimination against fields of endeavor: The license cannot bar use in a particular area of work, such as business or research.
- Distribution of the license: The rights must apply to recipients without requiring them to accept an additional license.
- The license must not be specific to a product: Rights cannot depend on the software being part of a particular product or distribution.
- The license must not restrict other software: It cannot impose restrictions on separate software distributed alongside the licensed work.
- The license must be technology-neutral: Its terms cannot depend on a particular technology or interface.
Is seeing the source code enough?
No. A code repository can be public while its terms deny recipients permission to reuse, modify, or redistribute the code. The OSD concerns the rights granted by the distribution terms. The OSI FAQ describes open-source software as software that can be freely accessed, used, changed, and shared; source availability without those freedoms does not meet that description. See the OSI FAQ.
Can open-source software be used commercially?
Yes. Open-source software can be used for commercial purposes and sold. The license still governs what a distributor may require of recipients; commercial use does not, by itself, permit a redistributor to add restrictions inconsistent with that license.
Does OSI approve licenses or software projects?
OSI’s formal approval applies to licenses, not to projects using them. A license may be evaluated against the OSD, but OSI-approved status follows a public review process: community discussion, a recommendation from the License Committee, and a decision by the OSI board. The OSI license list identifies licenses that comply with the OSD and have completed that review.
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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsSo a project’s use of an approved license is not a separate OSI certification of the project, and merely meeting the definition is not the same as completing OSI’s approval process.
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Is public-domain software an OSI-approved license?
No. Public domain is not a license for OSI to approve. The OSI FAQ notes that public-domain software may be effectively open source in practical terms in some circumstances, but it should not be described as using an OSI-approved license. The legal effect of a public-domain dedication can also depend on jurisdiction.
Where did the definition come from?
OSI was founded in 1998. Its history says the “open source” label emerged from a strategy session on February 3, 1998, and that the OSD was created around OSI’s launch by revising the Debian Free Software Guidelines and removing Debian-specific references. The history credits Bruce Perens with the original draft of those guidelines. See OSI’s history.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What this definition does not decide
The OSD explains the criteria for calling a software license open source under OSI’s definition; it is not a substitute for examining a particular license’s terms or the law that applies to a specific situation. For a concrete licensing question, read the actual license and seek jurisdiction-specific legal advice where needed.
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