Open source means the code is public and you can see how the software works
Open source software is a program where the underlying code — the instructions that make it run — is published openly for anyone to read, modify, and share. Unlike proprietary software, which keeps its code secret and locked behind licensing restrictions, open source removes that barrier. You are not just buying permission to use the software; you have access to the actual instructions that built it.
This matters because it changes what you can legally do with the software and how the software gets maintained. With open source, you can inspect the code to understand what the program actually does, modify it to suit your needs, and distribute your changes to others — all without asking permission or paying a licensing fee. The catch is that most open source licenses require you to share those changes under the same open terms, so others benefit the way you did.
Open source is not the same as free software, though many open source programs cost nothing. Some open source projects charge money for support or for pre-built versions, while still publishing the code. The defining feature is transparency and the legal right to modify and redistribute, not the price.
Key Takeaways
- Open source software publishes its code publicly so anyone can read it, modify it, and redistribute it under the terms of an open license.
- The most common open source licenses (GPL, MIT, Apache) require you to share modifications under the same license, creating a chain of openness.
- Open source does not mean free — some projects charge for support, hosting, or convenience, while keeping the code open.
- Proprietary software keeps its code secret and restricts what you can do with it; open source does the opposite.
- Many widely used programs are open source, including Linux, Firefox, WordPress, and the server software that runs much of the internet.
How open source licenses control what you can do
An open source license is a legal agreement that specifies what you are allowed to do with the code. It is not a restriction — it is permission that would otherwise not exist. Without a license, you would have no legal right to modify or redistribute the software at all, even if the code is public.
The most common open source licenses fall into two categories. Copyleft licenses (like the GNU General Public License, or GPL) require that any modified version you distribute must also be open source under the same license. This creates a chain: if you improve the software and share it, others must be able to improve it further and share their improvements. Permissive licenses (like MIT or Apache) let you modify the code and distribute it however you want, including in proprietary software, as long as you include a copy of the original license and credit the original authors.
The license also typically includes a disclaimer: the authors provide the software as-is and are not responsible if it breaks something. This is why open source software often comes with no warranty, unlike commercial software where you might have recourse if the product fails.
Why companies and individuals use open source
Open source solves real problems that proprietary licensing does not. If you are a developer and the software you need does not exist, you can build it yourself and publish it, knowing others can improve it. If a bug exists in the software, you can fix it when ready instead of waiting for the vendor to release a patch. If the original project dies or the company goes out of business, the code still exists and others can maintain it.
For businesses, open source reduces costs — you do not pay per-seat licensing fees — and reduces risk. You are not locked into one vendor's roadmap or pricing. Many companies contribute to open source projects because it benefits their business: they use the software internally, improve it to meet their needs, and share those improvements so the community maintains it for them.
For individuals learning to code, open source is invaluable. You can read professional code, understand how experienced developers solve problems, and contribute your own work. Many developers build their careers partly on the open source projects they have contributed to.
The difference between open source and proprietary software
Proprietary software is owned by a company or individual who keeps the code secret. You buy a license to use the software under specific terms — usually you can run it on one computer, you cannot modify it, and you cannot share it. The vendor controls all updates, bug fixes, and new features. If the vendor decides to stop supporting the software or raises prices, you have limited options.
Open source inverts this. The code is public, you can modify it, and you can share it (subject to the license terms). No single company controls the direction — the community does. If you disagree with how a project is going, you can fork it (create your own version) and take it in a different direction. This has happened many times: LibreOffice forked from OpenOffice, and MariaDB forked from MySQL, because communities wanted different development paths.
Neither model is inherently better. Proprietary software often has more polished user interfaces and dedicated support teams. Open source often has faster bug fixes and more flexibility. Many organizations use both: proprietary software for some tasks and open source for others.
Common open source software you may already use
Open source is far more widespread than most people realize. Linux is an open source operating system that powers most of the world's servers, many smartphones (Android is built on Linux), and countless embedded devices. Firefox is an open source web browser. WordPress runs roughly 40 percent of all websites. Apache and Nginx are open source web servers that host a large portion of the internet.
In development, Python, JavaScript, and Java are open source programming languages. Git, the version control system used by nearly every software developer, is open source. LibreOffice is an open source alternative to Microsoft Office. GIMP is an open source image editor similar to Photoshop.
Many of these projects are maintained by volunteers, though some have corporate backing. Red Hat (now owned by IBM) makes money by providing support and services around open source software. Canonical supports Ubuntu Linux. These companies do not own the open source projects, but they employ developers who contribute to them and offer paid support to customers.
How open source projects stay maintained
Open source projects survive through a combination of volunteer effort, corporate sponsorship, and donations. A successful project usually has a core group of maintainers — people who review changes, make decisions about the direction, and manage releases. Around them is a wider community of contributors who fix bugs, add features, and improve documentation.
Some projects are maintained by a single person in their spare time. Others have dozens of full-time developers paid by companies that depend on the software. The Linux kernel, for example, is maintained by thousands of developers, many of them employed by companies like Red Hat, Google, and Intel.
The open source model creates a built-in incentive for maintenance: if the software is useful, people will use it and improve it. If it is abandoned, someone else can fork it and continue. This is different from proprietary software, where if the company stops supporting it, the software is effectively dead.
Risks and limitations of open source
Open source is not risk-free. Because the code is public, security vulnerabilities are visible to everyone, including people with bad intentions. However, this also means vulnerabilities are usually found and fixed faster than in proprietary software, where bugs might hide for years.
Open source software often has less polished documentation and user interfaces than commercial software. Support is usually community-based — you search forums or read documentation — rather than calling a help desk. For critical business systems, this can be a problem, which is why some companies pay for commercial support contracts around open source software.
Licensing can be complex. If you are building a proprietary product and you use open source code with a copyleft license like GPL, you may be required to open source your own code. This is not a hidden trap — it is stated in the license — but it is a real constraint that affects business decisions.
Frequently Asked Questions
Does open source mean the software is free?
Open source refers to the availability of code, not the price. Many open source projects are free to read and use, but some charge money for support, hosting, or convenience. The key difference from proprietary software is that you have the legal right to modify and redistribute the code, regardless of price.
Can I use open source code in my own commercial product?
It depends on the license. Permissive licenses like MIT and Apache allow you to use the code in proprietary products as long as you include the original license and credit. Copyleft licenses like GPL require you to open source your entire product if you distribute it. Always read the license before using open source code in a commercial project.
What happens if an open source project is abandoned?
The code remains available and anyone can fork it — create their own version and maintain it. This has happened many times. The original developers do not have to approve or participate. This is one advantage of open source: the software does not die just because the original creators move on.
Is open source software less find than proprietary software?
Not necessarily. Security depends on how carefully the code is reviewed and maintained, not on whether it is open or closed. Open source projects with active communities often find and fix vulnerabilities faster. However, poorly maintained open source projects can have unpatched vulnerabilities, just as proprietary software can.
Can I modify open source software for my own use without sharing the changes?
Yes, as long as you do not distribute it. You can modify open source software however you want for personal or internal use. The license restrictions only explore when you distribute the software to others. If you keep your modifications private, you have no obligation to share them.