1.3 Open Source Software and Licensing (Weight: 1)
📘Linux Essentials (LPI 010-160)
1. What is Open Source Software?
Open source software is software whose source code (the human-readable instructions) is available for anyone to view, modify, and share.
- Source code: This is the “recipe” of the software. You can see how it works and change it if you want.
- Open source is often free, but the main idea is freedom, not just price.
IT example:
- Linux itself is open source. A system administrator can look at the kernel code, fix a bug, or improve it.
- Apache HTTP Server is open source. You can configure it to suit your organization’s needs because the source code is open.
2. What is Free Software?
Free software is software that gives you four important freedoms. The word “free” means freedom, not just no cost.
The four freedoms are:
- Freedom 0 – Run the program
You can run the software for any purpose.
Example: You can run MySQL database on your server for testing or production. - Freedom 1 – Study how it works
You can look at the source code to understand how it works.
Example: A developer can check how WordPress handles user login security. - Freedom 2 – Modify it
You can change the software to meet your needs.
Example: Customize Nagios monitoring system to send alerts differently. - Freedom 3 – Share it
You can give the original or modified version to others.
Example: Share a customized Ubuntu ISO with colleagues.
Remember: Open source and free software often overlap. Most free software is open source, and most open source software is free.
3. Why Licenses Are Important
Even if software is open source or free, you need permission to use, modify, or share it. Licenses tell you what you can and cannot do.
- License = legal rules for using software.
- Every open source software has a license attached.
4. Main Types of Open Source / Free Software Licenses
A. Copyleft Licenses
- They require you to share your changes under the same license.
- If you modify software and distribute it, you must make your changes open source too.
- Strong copyleft: All modifications and derivative work must be open source.
- Weak copyleft: Some parts can remain private (like libraries).
Examples:
- GNU General Public License (GPL) – strong copyleft
- Used by Linux kernel and GIMP.
- If you modify it and distribute it, your version must also be GPL.
- GNU Lesser General Public License (LGPL) – weak copyleft
- Used by some libraries, e.g., GTK.
- Programs using the library can be proprietary, but changes to the library itself must be LGPL.
B. Permissive Licenses
- They allow almost anything, including using the software in proprietary programs.
- You don’t have to share your changes.
Examples:
- MIT License – simple, flexible
- Used by Node.js and Express.js.
- Apache License 2.0 – includes patent protection
- Used by Apache Hadoop and Apache Kafka.
C. Public Domain / No License
- Some software is released to the public domain or without a license.
- You can use it freely, but no legal protection is guaranteed.
5. Key Things to Remember for Exams
- Open source ≠ always free – it means source code is available and modifiable.
- Free software focuses on freedom, not price.
- GPL = strong copyleft, MIT/Apache = permissive.
- Licenses protect your rights and tell you what you can legally do.
- Always check the license before using or distributing software in a business or project.
6. IT-Focused Examples for Better Understanding
| Software | License Type | What You Can Do | Example in IT |
|---|---|---|---|
| Linux kernel | GPL | Modify, redistribute your changes | Add a driver to a server kernel |
| Apache HTTP Server | Apache 2.0 | Modify, redistribute without sharing changes | Customize server for company website |
| MySQL | GPL | Modify, share your version under GPL | Optimize queries for internal database |
| Node.js | MIT | Modify, keep changes private or share | Build internal apps without open sourcing code |
| GIMP | GPL | Modify and redistribute modifications | Add a plugin for company graphics workflow |
7. Quick Exam Tips
- Be ready to match license type with its rules.
- Understand differences between copyleft and permissive licenses.
- Know examples of open source software and which license they use.
- Remember freedom vs price – “free” is freedom, not always zero cost.
This covers everything necessary for 1.3 Open Source Software and Licensing → Open source and free software licenses in the LPI 010-160 exam.
