What Is Open Source Software and Why Does It Power the Internet?

Android, the Linux kernel, Firefox, VS Code, Python, React, MySQL, WordPress — these are among the most widely used software products in the world. They’re all open source.

Open source software is not a niche concept. It is the foundation of the modern internet and most of the technology you use every day.

What “Open Source” Means

Open source software is software whose source code — the human-readable instructions that make it work — is publicly available for anyone to view, use, modify, and distribute.

The opposite is proprietary (or “closed source”) software, where the source code is owned and kept secret by the company. Windows and macOS are proprietary. iOS is proprietary. Microsoft Office is proprietary.

Open source doesn’t necessarily mean free (as in free beer) — though most open source software is available at no cost. It means free as in freedom: freedom to inspect the code, modify it, and distribute your changes.

How Open Source Development Works

A project typically starts with one or a few developers who release their code publicly. The project lives on a platform like GitHub, where anyone can see the code.

From there, other developers can:

• Fork the project: make their own copy to modify independently
• Contribute: submit changes (called pull requests) back to the original project
• File issues: report bugs or request features
• Use it: incorporate it into their own software, per the license terms

Major projects develop communities of contributors — sometimes thousands of developers across dozens of countries. Linux, for example, has had contributions from engineers at Google, Microsoft, Intel, Amazon, and countless independent developers.

Why Companies Contribute to Open Source

A reasonable question: why would companies contribute code to projects their competitors also use?

Shared infrastructure costs: If 50 companies all need a reliable database, it’s cheaper for all of them to share the cost of maintaining an open source database than for each to build their own.

Attracting talent: Developers use open source projects. Companies that visibly contribute to projects developers care about gain credibility and attract good engineers.

Standards and influence: Contributing to open source projects you depend on lets you shape their direction. Google’s massive contributions to the Linux kernel, Android, and Chrome give Google influence over how those technologies evolve.

Community testing: An open source project used by millions of developers gets tested against more edge cases, hardware configurations, and use cases than any internal test suite could cover.

Notable Open Source Projects

Linux: The kernel (core) of most servers, Android phones, and supercomputers. Created by Linus Torvalds in 1991. Probably the most important piece of open source software in existence.

Apache / Nginx: Web server software that serves most websites on the internet.

MySQL / PostgreSQL: Open source databases powering millions of applications, including WordPress.

Python: One of the most popular programming languages, used in data science, AI, automation, and web development.

React / Vue / Angular: The front-end JavaScript frameworks covered elsewhere on this site.

VS Code: Microsoft’s code editor, open source and wildly popular with developers.

WordPress: Powers 43% of all websites. Open source PHP application.

Firefox: Open source browser from Mozilla, one of the few major browsers not built by a tech giant with advertising interests.

Open Source Licenses: The Legal Framework

Not all open source licenses are the same. The license determines what you can and can’t do with the software:

Permissive licenses (MIT, Apache, BSD): Use, modify, and distribute freely, including in proprietary products. You just have to include the original copyright notice. Most commercial software incorporating open source uses permissively licensed components.

Copyleft licenses (GPL): If you distribute software that includes GPL-licensed code, your entire distribution must also be released under the GPL. Designed to prevent companies from taking open source code and “closing” it. Linux uses the GPL — this is why Android is open source.

Creative Commons: Used for creative works (documentation, art) rather than code.

For most purposes, MIT-licensed software can be used freely in any project. GPL-licensed software requires more attention to licensing obligations.

The Security Question

A common objection: if the code is public, can’t attackers find vulnerabilities more easily?

In practice, the opposite tends to be true. More eyes on code means more people finding and reporting vulnerabilities. Security researchers globally audit open source projects constantly. Flaws are fixed publicly and transparently.

Proprietary software has vulnerabilities too — they’re just hidden from scrutiny. The discovery often comes from attackers, not defenders. Open source vulnerabilities are more likely to be found by researchers and patched before exploitation.

The caveat: small, under-maintained open source projects can be vulnerable simply due to neglect. The xz Utils backdoor in 2024 illustrated this risk for critical but under-resourced projects.

---

Open source is not idealism — it’s an engineering and economic model that has proven more effective than any alternative at building the foundational infrastructure of the internet. Understanding it helps you understand why the technology world works the way it does.