Can open source software be changed?

Can open source software be changed? Yes, unlike proprietary code

Understanding can open source software be changed is essential for developers seeking to customize their digital tools without legal restrictions. This flexible model encourages innovation and provides significant advantages over closed systems. Learning the specific rights associated with these projects helps you avoid technical limitations and ensures your development process remains efficient.

Can open source software be changed?

Yes, can open source software be changed because the ability to study, modify, and improve the source code is its defining characteristic. This freedom is not just a technical possibility - it is a legal right granted by specific licenses like MIT, GPL, or Apache. However, how you share those changes depends entirely on the specific rules of the license governing the original project.

In my first year as a developer, I thought open source was just free software I could use. It took me a few months and a very messy fork of a library to realize that the power isnt in the price tag, but in the permission to fix things.

I spent three days trying to patch a bug in a styling library, convinced I was breaking some hidden law. Turns out, that is exactly what the creators wanted me to do. But there is a catch that most beginners miss - one that can lead to significant legal headaches if you plan to share your work. I will reveal that specific trap in the licensing section below.

The legal right to modify: How licenses work

When you download open source software, you are essentially entering a contract that says you can open the hood, look at the engine, and swap out the parts. Unlike proprietary software (like Windows or Photoshop), where the source code is a trade secret, open source projects publish their code for everyone to see. This open-access model has led to massive adoption, with roughly 90% of modern software stacks containing open source components in some capacity. ^[1]

While you can you edit open source software for personal use without telling anyone, the rules change when you redistribute that modified version. For example, licenses fall into two main categories: permissive and copyleft. Permissive licenses (like MIT) are very relaxed - you can change the code and even keep your changes secret. Copyleft licenses (like the GPL) require that if you share your modified version, you must also share your new code under that same license. It ensures the software stays open forever. Much different than just viewing code.

Open source vs. Source-available: The modification gap

A common mistake is assuming that if you can see the code on GitHub, you have the right to change it. This is not always true. Many companies use source-available licenses. These allow you to read the code for educational purposes or security audits, but they strictly forbid you from making changes or using it in a competing product. It is a difference between open source and source available modification that trips up even experienced engineers.

I remember a colleague who spent weeks customizing a source-available database tool for a client project, only to realize at the last minute that the license prohibited any derivative works. We had to scrap three weeks of work. It was brutal. Always check the LICENSE file in the root directory - if it is not an OSI-approved (Open Source Initiative) license, you might be looking but not touching. This oversight is a leading cause of open source license modification rights issues in corporate environments as more companies move to restricted models to protect their business. ^[2]

Can you sell modified open source software?

Yes, can I sell modified open source software, but there is a major commercial hurdle. If the software is under a copyleft license (like GPL), you must provide the source code to anyone who buys it. Since they then have the code, they could technically give it away for free. This makes the traditional pay-per-license model very difficult for open source. Most companies instead sell support, hosting, or enterprise features that are not part of the open core.

Wait a second. If anyone can give it away, how do people make money? They sell convenience. Many companies using open source tools would rather pay for a managed service than spend their own engineering hours maintaining a modified version.^[3] The value shifted from the code itself to the expertise required to run it. Here is that catch I mentioned earlier: the Copyleft Trap. If you combine your secret, proprietary code with GPL-licensed code, you might be legally forced to open-source your entire project. It is called the viral nature of the GPL. Be careful what you mix.

Modification Rights: Open Source vs. Source-Available

Understanding whether you can legally change code depends on the specific license type. Here is how they compare in practice.

Open Source (MIT/Apache)

• Can be used in commercial products; changes can often remain private.
• Modify and use internally without any obligation to share.
• Full rights to modify any part of the source code for any purpose.

Open Source (GPL/Copyleft)

• Difficult to sell directly as the modified source must be made public.
• Modify freely for yourself without sharing code.
• Full rights to modify, but changes are 'viral' if distributed.

Source-Available (Restricted)

• Almost always requires a paid commercial license for any modification.
• Strictly limited to the terms of the specific license provided.
• Usually prohibited; viewing is allowed, but 'derivative works' are not.

The Forking Friction: Hùng's Custom Dashboard

Hùng, a junior dev at a startup in Ho Chi Minh City, found an open source dashboard that was 90% perfect. He needed to change the data visualization logic to support a niche Vietnamese payment gateway. He felt confident - it was open source, after all.

First attempt: He 'hard-coded' the changes directly into the library files. Result: When the original library updated a week later, all of Hùng's changes were wiped out, crashing the staging server. He spent a frantic weekend trying to recover his work.

He realized he shouldn't just edit the files, but 'fork' the repository or use a wrapper. He created a clean fork on GitHub, properly documented his changes, and maintained it separately from the main project updates.

The custom dashboard now handles 10,000 transactions daily. Hùng's fork actually became popular, and within 3 months, his performance improvements (reducing load times by 40%) were merged back into the original project.