Open Source

In Turkish: Açık Kaynak
Pronunciation: OH-pun SORSS

Updated October 3, 20262 min read

In short

Open source software is software whose source code is published under a license that lets anyone use, study, modify and share it.

What is open source software?

The idea grew from the free software movement that Richard Stallman launched with the GNU Project in 1983, which emphasized users' freedom to run, change and share programs. The term open source was introduced in 1998, the same year the Open Source Initiative was founded, to describe the practical benefits of shared code to businesses. Its Open Source Definition sets out which licenses qualify.

Much of the modern software world runs on open source: Linux, Git, Python, Node.js, PostgreSQL, Kubernetes, React and most of the libraries installed through npm and pip. Companies use it because it is free to adopt, can be inspected and audited, can be modified when needed, and avoids being locked into one vendor.

Projects are usually hosted on platforms such as GitHub or GitLab, where anyone can report issues and propose changes through pull requests that maintainers review. Foundations such as the Linux Foundation and Apache Software Foundation provide neutral homes for big projects, and many maintainers are funded by companies or donations, though many popular projects still rely on a few volunteers.

A common misconception is that open source means free of any rules. Every project has a license with conditions, such as keeping copyright notices or, for copyleft licenses, sharing changes under the same terms. Another is that open source is automatically secure; public code can be reviewed by anyone, but only if someone actually does it.

Key takeaways

Open source code can be used, studied, modified and shared under its license.
The term dates from 1998; the free software movement began in 1983.
Linux, Git, Python, Kubernetes and React are open source.
Contributions come through issues and pull requests reviewed by maintainers.
Licenses still set conditions, and security depends on real review.

Readers ask

What is the difference between open source and free software?

They mostly describe the same licenses. Free software, as defined by the Free Software Foundation, emphasizes users' freedoms as an ethical principle; open source emphasizes the practical benefits of open development. FOSS combines both terms.

Can I use open source software in a commercial product?

Usually yes, but you must follow the license. Permissive licenses such as MIT and Apache 2.0 require little more than keeping notices, while copyleft licenses such as the GPL may require you to release your own source code under the same license.

How can I contribute to open source?

Start with a project you use, read its contributing guide, and look for issues labeled for newcomers. Fixing documentation, reproducing bugs and adding tests are valuable first contributions.