What Is Open-Source Software? And Why Half the Internet Runs on It
✦ Key takeaways
- Open source means a program’s code is available for anyone to read, modify and redistribute.
- Often free, but not always; ‘open source’ is about freedom, not price.
- The license decides what’s allowed: GPL keeps derivatives open, MIT is more permissive.
- You use it daily: Android, your browser and most web servers run on open projects.
Imagine a recipe written out in full and posted publicly: anyone can read it, cook it, improve it, then publish their own version. Open-source software works the same way, but with code. The ‘source code’ is the set of instructions programmers write before it becomes a running program; when it’s open, anyone may inspect, modify and redistribute it under the license terms.
This is the opposite of closed (proprietary) software like Windows, where you get a ready-to-run program while the code stays a company secret.
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Open source doesn’t always mean free
This is the biggest point of confusion. ‘Open source’ is about freedom: to read, change and share. Much of it is indeed free of charge, but a company can sell a paid edition with support and services while the code stays open. The famous line: ‘free as in speech, not free as in beer’.
The license is the heart of it
A license is a legal contract defining what’s allowed. Two main families: ‘permissive’ licenses (like MIT and Apache) let you use the code even inside a closed commercial product as long as you credit the source; and ‘copyleft’ licenses (like GPL) require any derivative to stay open source too, guaranteeing continued openness.
Table: open vs closed
| Criterion | Open source | Closed source |
|---|---|---|
| Code visibility | Public | Secret |
| Modification | Allowed | Forbidden |
| Price | Often free | Usually paid |
| Security | Reviewed by thousands | Depends on the vendor |
| Examples | Linux, Firefox | Windows, Photoshop |
You use it today without knowing
Android is built on the open Linux kernel, most internet servers run Linux with Apache or Nginx, and Chrome is based on the open Chromium project. Even the Python language and the MySQL database are open. In practice, the internet’s infrastructure runs on open projects built by volunteers and companies together.
A practical tip
Before buying software, look for a mature open-source alternative: LibreOffice instead of Office, GIMP instead of Photoshop, VLC for media. It can save money and give you more control. And if you build a product, read the license of every library you use carefully — a violation can cost you legally.