Free and open-source software (FOSS)
The essential freedoms
Free software is software based on four essential freedoms:1
- Freedom 0: The freedom to run the program for any purpose. You can use the software however you want, without restrictions.2
- Freedom 1: The freedom to study how the program works, and change it to make it do what you wish. Access to the source code is a prerequisite for this freedom. (Source code is the human-readable instructions that make up the software.)
- Freedom 2: The freedom to create and distribute copies of the software. You can share the software with your friends, colleagues, or anyone else.
- Freedom 3: The freedom to create and distribute modified copies of the software. This allows anyone to build upon and improve the software.
Free software can be as well-written, robust, and feature-rich as any commercial software. In many cases, it is objectively better than proprietary counterparts, as it's often developed by a community of passionate contributors, who are driven by a shared vision of creating something better for everyone.
Why is it important?
Free and open-source software (FOSS) is important because it empowers individuals and communities to have control over their technology.
How is it better than proprietary software?
FOSS is often better than proprietary software because it benefits from being: transparent and more collaborative.
Here's a quick table to show you what we mean:
| Free Software | Open Source | Proprietary | |
|---|---|---|---|
| Control | Users have control over their data and applications | Users have control over their data and applications | Companies have control over their data and applications |
| Transparency | Source code is available for anyone to view, modify, and build upon | Source code is available for anyone to view, but not necessarily redistributable | Source code is not necessarily available or redistributable |
| Motives | Transparent and free. Not affected by profit motives. | Transparent, but sometimes affected by profit motives. | Almost always affected by profit motives, or other ideologies. |
| Customizability | Customizable by nature, users can modify and build upon the software. | Customizable by nature, but not necessarily redistributable. | Proprietary impose a one-size-fits-all solution. |
The licensing is important in this context because it determines who can use and modify the software. For example, a proprietary license might restrict anyone from redistributing original or modified versions of the software, while a free software license will allow anyone to modify and build upon it. This can have a significant impact on how the software is developed and used.
This is an important distinction if you are confused about the term "software license".
In proprietary software, you usually pretty much don't own anything, and you don't have any rights to whatever you're using. You are usually granted an access to use the software but not "ownership" over it. What's more, you can only use it as long as you respect the license terms. Some proprietary software can revoke your access if you don't respect the license terms or if they change them.
When we talk about open-source or free software licenses, we are not talking about the same "software licenses". We are talking about the licensing of the code itself.
In free software, there aren't any EULAs or other restrictions on how you can use the code. You are free to modify and build upon it as long as you respect the license terms.
Open source doesn't mean free software
While often used interchangeably, there's a subtle difference:
- Free Software focuses on the ethical freedom of users. It's about the moral imperative to give users control over the technology they use. The FSF is the main organization promoting this philosophy.
- Open Source focuses on the practical benefits of making source code available. It emphasizes collaboration, innovation, and quality. The Open Source Initiative (OSI) is the main organization promoting this approach.
Most free software is also open source, and most open source software is also free software. There sometimes are some differences in their philosophies and licensing approaches. The key difference is usually the reason for making the source code available.
Common licenses
The following table does not constitute legal advice. It is for informational purposes only.
The following licenses contain free software licenses but also common open-source ones.
| License | Copyleft | Redistribution | Explanation |
|---|---|---|---|
| MIT | None | Allowed | One of the most permissive licenses with no copyleft. MIT-licensed projects are attractive to companies that want to benefit from open-source innovation while keeping their own code proprietary. |
| Apache 2.0 | None | Allowed | Permissive license with explicit patent grant; free redistribution. |
| GPL v2 | Strong | Allowed with source | A strong copyleft license; redistribution is only allowed when the source is provided. |
| GPL v3 | Strong | Allowed with source | An upgrade to the GPL v2. It closes the tivoization loophole by requiring devices that run GPL software to allow users to run modified versions, protects users against patent claims with a built-in grant and termination clause. |
| GPL-only | Strong | Allowed with source | Strong copyleft; the software is licensed exclusively under a specific version of the GNU GPL, and no later versions of that license are permitted. |
| LGPL | Soft | Allowed with source | A relaxed version of the GPL. The idea is to let developers use and distribute library code (or other "linkable" pieces) inside their own software, whether open-source or proprietary, while still protecting the freedom of the library itself. |
| AGPL | Strong | Allowed with source | A stricter version of the GPL. Requires source disclosure for redistribution but also for network use. |
| MPL 2.0 | File-level | Allowed with source for modified files | File-level copyleft; requires source disclosure for modified files; free redistribution. |
Disambiguation with freemium
When companies describe their software as "free", it often refers to freemium software3, which is a form of proprietary software. It usually comes with arbitrary limitations, like limited features or time limits (frequent in mobile games), unless the user pays for a subscription or license.
Common fallacies
"Open-source doesn't mean security"
It is quite common to see people online (often so-called "experts") who claim that open-source software is pointless. Sadly, these arguments often overlook the strengths of open-source development.
A common myth is that transparent code is dangerous as anyone can potentially find vulnerabilities without informing the developers. This aims to defend the bad practice of security by obscurity
However, this argument is often misleading. People sometimes say open-source software is not secure to distract from problems with proprietary software.
Some worry that open-source projects are unstable. They think many different people working on a project makes it less reliable. Many contributors can actually make the software stronger.
Open-source projects are open for anyone to see. Some people act like this means no one checks the code. This isn't true. The open nature simply subjects them to scrutiny, and is better than a security by obscurity model.