Terms and Definitions
Open source (common short-hand: OS): A transparent technology creation, development, collaboration, and distribution model, where the source, deliberation, decision-making, and roadmap of the technology are all presented and conducted publicly. It is not a type of company, business, or business model.
Open source software (common short-hand: OSS or FOSS--Free and Open Source Software): Software made generally available under a copyright license that meets the Open Source Definition, as defined by the Open Source Initiative.
Source Available Software: Software made generally available in source code form under a copyright license that does not meet the Open Source Definition. This type of license is also called a limited source code license.
Example: MongoDB under the Server Side Public License (SSPL), MariaDB under the Business Source License (BSL).
Commercial open source software (common short-hand: COSS): A category of companies or business units that commercializes open source technology. The existence of COSS depends on the existence of the corresponding open source technology but not vice versa. Often times, these businesses are founded or led by the core maintainers and committers of the open source technology from which they are built. (See different definitions of "Maintainer" and "Committer" below)
Example: see the Commercial Open Source Software Index (COSSI), a list of COSS companies that have reached $100 million USD in annual revenue.
Public Domain Software: Software made generally available with no copyright license conditions at all.
Open Core: A business model, or subset of the COSS company category, where an open source project is the foundation (or “core”) from which a commercial product is built and copyrighted under a proprietary license (as opposed to an open source license). The proportion of open and proprietary in a product offering, depends on the particular use case, technology, and business value. (See below different definitions of "Project" and "Product". See this post for a more detailed discussion of “open core” implementation.)
Single-Vendor: A term that describes when an open source project is primarily developed and commercialized by a single business entity, commonly known as a vendor.
Multi-Vendor: A term that describes when an open source project is developed and commercialized by more than one business entity.
Project: A piece of technology that is created, developed, and maintained based on open source methodology and can be independently used for its functionality. It is not commercially licensed or sold directly, but are often supported or serviced via commercial agreements between user and service provider.
Product: A commercially licensed product built on top of an open source project that are packaged, distributed, and sold to customers of the COSS entity that built this product. It is a discreet but related piece of technology to its open source project base.
Benevolent Dictator For Life (common short-hand: BDFL): An open source community governance model where a single person, typically the creator of the project, makes most of the major decisions associated with the project.
Maintainer: A developer whose main responsibility is to drive and manage the roadmap and development of an open source project by engaging in activities such as code review, roadmap, governance, and community and ecosystem building. It’s typically considered a community position with the most responsibility and power. It is also often used interchangeably with "Committer" (see below), because both roles have commit access to the project and can review and merge changes from a "Contributor" (see below).
Committer: A developer whose main responsibility is to build core features and improvements of an open source project and conduct code review of other contributions. It’s typically considered a community position with the second most responsibility and power, but it's also often used interchangeably with "Maintainer" (see above), because both roles have commit access to the project and can review and merge changes from a "Contributor" (see below).
Contributor: A developer who makes either regular or ad-hoc contributions to the code base of an open source project, reviewed and merged by either the maintainer or committer. The scale and difficulty of contributions vary widely, from fixing major bugs or developing a feature, to fixing typos and formatting in the documentation.
Governance: A set of rules and procedures, similar to a corporation’s bylaws or a country’s constitution, that outlines how an open source project makes technical and community decisions, and how individual developers become maintainers, committers, contributors, or other community roles. These rules and procedures typically exist in a public document in either the project’s code repository or website.
Foundation: A not-for-profit entity that hosts open source projects inside a neutral organization, separated from any commercial entities that monetize the projects. The foundation is typically responsible for the governance, legal, trademark, and other administrative work associated with managing an open source project. It also engages in marketing, educational, and ecosystem-building activities for the projects it hosts.
A foundation often plays a key role in ensuring the sustainability and longevity of open source projects, independent of whether the projects are being monetized or commercialized by companies.
Code of Conduct: A set of community policies and norms articulated and applied as the basis to manage, moderate, and adjudicate the behaviors of and communications between members of an open source community. It is usually in the form of a public document in either the project’s code repository or website.