Popular Open Source Software Examples

In the previous chapter, "Pros and Cons of Open Source," we explored the theoretical benefits and drawbacks of software whose source code is freely available to the public. We talked about how it saves money, boosts security through transparency, and relies on community support.

But theory only takes us so far. To truly master this topic, you need to know what open-source software looks like in the real world. You probably use open-source technologies every single day without even realizing it. When you browse the web on your phone, watch a video on your laptop, or even when you simply load a webpage, open-source software is working behind the scenes.

In this chapter, we are going to walk through the most famous, globally used examples of open-source software. We will break them down by category: Operating Systems, Web Browsers, Office Suites, Creative Tools, and finally, the "Backend" tools that power the internet.

By the end of this chapter, if you see a software name in an exam option, you will know exactly what it does, whether it is open-source, and why it matters.

1. Operating Systems: The Foundation of Your Device

An operating system (OS) is the master software that manages all the hardware and other software on a computer. Without an OS, your laptop or smartphone is just an expensive brick of plastic and metal. While Microsoft Windows and Apple macOS are proprietary (closed-source), the open-source world has produced some of the most powerful operating systems on the planet.

Linux: The King of Open Source

If there is one name you must associate with open-source software, it is Linux. Created in 1991 by a Finnish student named Linus Torvalds, Linux was built as a free alternative to expensive, proprietary operating systems used by large universities and corporations.

Here is a crucial distinction that exams love to test: Linux itself is technically just a kernel. The kernel is the absolute core of the operating system—the engine of the car. But a car needs seats, a steering wheel, and a dashboard before you can drive it.

Because Linux is open-source, different organizations take the Linux kernel, add a user interface, file managers, and built-in apps, and release it as a complete package. These complete packages are called Linux Distributions (or "distros" for short).

Here are the most famous Linux distributions you should recognize:

• Ubuntu: The most popular and user-friendly Linux distribution for everyday desktop computers and laptops. If a beginner wants to try Linux, they usually install Ubuntu.
• Linux Mint: Another highly popular, easy-to-use distribution designed to look and feel a bit like Microsoft Windows, making the transition easier for new users.
• Red Hat Enterprise Linux (RHEL): A heavy-duty version of Linux used by massive corporations and governments to run their servers. While the source code is open, Red Hat charges companies for customer support and maintenance.
• Kali Linux: A specialized distribution packed with security and hacking tools, used globally by cybersecurity professionals to test network defenses.

Android: The Open-Source Giant in Your Pocket

You might be surprised to learn that the most widely used operating system in the world—running on billions of smartphones—is open-source. Android is actually based on a modified version of the Linux kernel.

Google leads the development of Android through the Android Open Source Project (AOSP). Anyone, from a massive company like Samsung to a solo developer in their bedroom, can download the AOSP code for free, modify it, and build their own smartphone operating system.

However, there is a catch that you should understand: While the base Android operating system is open-source, the Google apps you are used to—like Google Maps, the Google Play Store, and Gmail—are proprietary. This bundle of apps is called Google Mobile Services (GMS).

So, when Samsung or OnePlus builds a phone, they take the free, open-source Android base, customize the look of it, and then sign a commercial agreement with Google to include the proprietary Google Play Store and apps.

2. Web Browsers: Your Window to the Internet

A web browser is the application you use to access websites. While Internet Explorer and Apple's Safari are proprietary, the open-source community has built browsers that revolutionized how we use the internet.

Mozilla Firefox

Before Google Chrome existed, Microsoft's Internet Explorer dominated the web. It was slow, prone to crashing, and completely closed-source. In the early 2000s, a non-profit organization called Mozilla released Firefox.

Firefox was a revelation. It was fast, introduced tabbed browsing (opening multiple websites in one window), and most importantly, it was 100% open-source. Because the code was public, thousands of developers around the world contributed to making it faster and more secure. Today, Firefox remains the flagship champion of the open web, prioritizing user privacy and refusing to track user data the way corporate browsers often do.

Chromium (The Engine Behind Chrome)

This is a very common area for confusion, so let's clear it up. Google Chrome is the most popular web browser in the world today. Google Chrome is proprietary software. You cannot see or modify its source code.

However, Google Chrome is built on top of an open-source project called Chromium.

Google maintains the open-source Chromium project. When Google wants to release a new version of Chrome, they take the free Chromium code, add their proprietary tracking, automatic updates, and closed-source media players, and release it as Google Chrome.

Because Chromium is open-source, other companies can use it too! In fact, Microsoft's Edge browser, the privacy-focused Brave browser, and the Opera browser are all built using the open-source Chromium code.

• Chromium: Open-source (The engine).
• Google Chrome: Proprietary (The engine + Google's closed-source additions).

3. Office Suites: Getting Work Done for Free

For decades, if you wanted to type a document, build a spreadsheet, or make a presentation, you had to buy Microsoft Office (Word, Excel, PowerPoint). This was expensive, especially for students and small businesses. The open-source community solved this by creating free, fully compatible alternatives.

LibreOffice

LibreOffice is the most popular open-source office suite in the world. It is completely free to download, has no subscription fees, and is maintained by a non-profit called The Document Foundation.

LibreOffice can open, edit, and save Microsoft Office files (like `.docx` or `.xlsx`), making it incredibly easy for people to switch. Exams frequently test your knowledge of the specific applications within LibreOffice by comparing them to Microsoft Office.

Here is the direct comparison you need to memorize:

• LibreOffice Writer: The word processor. (Equivalent to Microsoft Word).
• LibreOffice Calc: The spreadsheet application. (Equivalent to Microsoft Excel).
• LibreOffice Impress: The presentation software. (Equivalent to Microsoft PowerPoint).
• LibreOffice Base: The database management tool. (Equivalent to Microsoft Access).
• LibreOffice Draw: A vector graphics and flowchart tool. (Equivalent to Microsoft Visio).

Apache OpenOffice

You might also hear the name OpenOffice. Historically, OpenOffice was the original massive open-source office suite. However, due to corporate disagreements when the company Sun Microsystems (which sponsored OpenOffice) was bought by Oracle, the community of developers rebelled.

They took the open-source code of OpenOffice, copied it, and renamed their new version LibreOffice. This process of taking open-source code and splitting it into a new, separate project is called a fork. Today, LibreOffice is actively updated and widely used, while OpenOffice receives very few updates.

4. Media and Graphics: The Creative Tools

Professional creative software like Adobe Photoshop or Adobe Premiere Pro costs hundreds of dollars a year in subscription fees. Open-source alternatives provide powerful tools to artists, photographers, and video editors at zero cost.

VLC Media Player

If you have ever downloaded a video file that your computer refused to play, someone probably told you to "just download VLC."

VLC Media Player (easily recognized by its orange traffic cone logo) is a free and open-source cross-platform multimedia player. It is famous because it can play almost any audio or video file format in existence without needing you to download extra plugins. It is developed by the VideoLAN project, a non-profit organization, and is a perfect example of open-source software solving a universal problem (file compatibility) for free.

GIMP (GNU Image Manipulation Program)

GIMP is the open-source world's answer to Adobe Photoshop. It is a highly sophisticated image editor used for photo retouching, image composition, and graphic design.

Because it is open-source, users have created thousands of free plugins and scripts to add new features to GIMP over the years. While it has a steeper learning curve than some basic photo editors, it is the undisputed king of free, open-source raster graphics editing.

Blender

Blender is a free and open-source 3D computer graphics software toolset. It is used for creating animated films, visual effects, art, 3D printed models, motion graphics, and even video games. It is so powerful that professional Hollywood studios and major game developers use it, proving that open-source software can compete at the absolute highest levels of industry.

5. Backend Tools: The Invisible Workhorses of the Internet

So far, we have talked about "frontend" software—applications you click on and interact with directly on your screen. But the true dominance of open-source software lies in the "backend."

The backend refers to the servers, databases, and infrastructure that live in massive data centers and make the internet work. When you open a website, your browser (frontend) talks to a server (backend). The vast majority of the internet runs on open-source backend software.

The Apache HTTP Server

When you type a website address (like `www.jkexam.com`) into your browser and hit Enter, your computer sends a request across the internet to a physical computer sitting in a server room. That physical computer needs a piece of software to receive your request, find the correct webpage files, and send them back to you.

This software is called a Web Server.

The Apache HTTP Server (usually just called "Apache") is one of the oldest, most reliable, and most widely used open-source web servers in the world. For over two decades, it has been the backbone of the World Wide Web.

MySQL and MariaDB (Databases)

Websites are not just static pages of text anymore; they are dynamic. Think about an e-commerce site: it has to store millions of user accounts, passwords, product prices, and order histories. All of this data is stored in a Database.

MySQL is the world's most popular open-source relational database management system. It organizes data into neat tables (like a highly advanced Excel spreadsheet) so that websites can instantly retrieve the exact information they need.

Analogy time: Imagine a restaurant.

• Your web browser is the Customer looking at the menu.
• The Apache Web Server is the Waiter. It takes your order (your request to see a page) and brings the food back to your table.
• The MySQL Database is the Kitchen Pantry. It is where all the raw ingredients (data, passwords, text) are securely stored and organized.

(Note: Just like OpenOffice, MySQL was bought by a large corporation. The original creators were worried the corporation might ruin it, so they "forked" the open-source code and created a clone called MariaDB. Both MySQL and MariaDB are heavily used open-source databases today).

WordPress (Content Management System)

If you want to build a website today, you don't need to write raw code from scratch. You can use a Content Management System (CMS).

WordPress is an open-source CMS that powers over 40% of all websites on the entire internet. From small personal blogs to the official websites of massive news organizations and governments, WordPress provides a free, open-source framework to publish content online.

The LAMP Stack

In the IT industry and in exams, you will frequently see these backend tools grouped together into an acronym called the LAMP stack. A "stack" is just a bundle of software that works together to run a website.

The LAMP stack is entirely open-source and consists of:

• Linux (The Operating System running the server computer)
• Apache (The Web Server handling the requests)
• MySQL (The Database storing the information)
• PHP / Python / Perl (The open-source programming languages used to write the website's logic)

If a company uses the LAMP stack, they can build and host a massive, complex website without paying a single rupee in software licensing fees.

6. Programming Languages

It is worth briefly noting that the languages developers use to write software are themselves almost entirely open-source today.

If a programming language were proprietary, a company could charge developers a fee just for the right to write code in that language. To encourage innovation, the tech industry relies on open-source languages.

• Python: Currently the most popular programming language in the world, heavily used in Artificial Intelligence, data science, and web development. It is 100% open-source.
• PHP: The open-source language that powers WordPress and a huge portion of the dynamic web.
• Java (OpenJDK): While Oracle owns a proprietary version of Java, the core language is available as an open-source project called OpenJDK, which is used globally to build enterprise software and Android apps.

Quick Revision

Here are the high-yield facts to scan before your exam:

• Linux is an open-source operating system kernel. Complete versions of it are called distributions (e.g., Ubuntu, Linux Mint, Red Hat).
• Android is an open-source mobile operating system based on Linux, maintained by Google via the AOSP (Android Open Source Project).
• Mozilla Firefox is a fully open-source web browser.
• Chromium is the open-source engine that powers the proprietary Google Chrome browser, as well as Microsoft Edge.
• LibreOffice is the premier open-source office suite. Remember its components: Writer (Word), Calc (Excel), Impress (PowerPoint), Base (Access).
• VLC Media Player is a universally used open-source tool for playing almost any audio or video file.
• GIMP stands for GNU Image Manipulation Program and is the open-source alternative to Adobe Photoshop.
• Apache is an open-source web server that processes requests and delivers web pages to users.
• MySQL is a highly popular open-source relational database used to store website data.
• The LAMP Stack is a famous bundle of open-source web technologies: Linux, Apache, MySQL, and PHP.