What is the difference between free software and open source software?

There are several types of software.
Proprietary software, also known as commercial or non-free software, is software whose source code is not accessible to the public, accompanied by restrictive licences that limit its use, modification and redistribution by users. They are generally sold in the form of paying licences, with no possibility of redistribution, and are tightly controlled by their developers or companies. Such software includes operating systems such as Microsoft Windows, office suites such as Microsoft Office, and graphics programs such as Adobe Photoshop, often chosen for their professional support and widespread adoption.

There is also free software and open source software, two concepts that are often associated.
Free software and open source software share many similarities, but they are sometimes distinguished by certain differences, mainly in terms of philosophy, the licensing criteria being virtually identical in both cases.

What is Free Software?

Free Software, as defined by the Free Software Foundation (FSF), is software that grants its users four fundamental freedoms:

1. The Freedom to Run the Program: Users have the right to run the software for any purpose. This freedom implies that no type of use of the software should be restricted or prohibited.

2. Freedom to Study and Modify the Program: Users must have access to the source code of the software and the ability to modify it. This freedom is crucial to enable a personal understanding of the software and to allow adaptations to individual needs.

3. Freedom to Redistribute Copies: This freedom allows users to share copies of the software with others. It plays an important role in disseminating the software and helping others..

4. Freedom to Distribute Modified Versions: Users must be able to distribute their modified versions to others, giving the community the opportunity to benefit from the improvements. This freedom is fundamental to the creation of an active and collaborative community around the software.

Free software should not be confused with freeware, which can be used, copied and distributed free of charge, but whose source code is not necessarily accessible or modifiable.

Free software is also distinguished by its philosophy and ethics, which emphasise freedom and community cooperation. This approach goes beyond the simple use of software and encompasses considerations of users’ control over technology and their ability to collaborate and share knowledge.

What is open source software?

Open source software is defined by free access to the source code and a licence that allows users to modify, improve and redistribute the software. Here are the main characteristics of open source software:

1. Access to the source code: The software’s source code is available to everyone. This allows users and developers to study how the software works and adapt it to their needs.

2. Freedom of Modification: Users have the freedom to modify the software source code. This encourages innovation and the adaptation of the software to specific contexts.

3. Free Redistribution: Users can freely redistribute copies of the original software or modified versions. This feature is essential to encourage the sharing and dissemination of the software.

4. Permissive licence: Open source software is distributed under licences that respect these freedoms. These licences may vary in their precise terms, some being more permissive (such as the MIT License or the Apache License) and others imposing conditions to maintain the open source nature of the software in all derived versions (such as the GNU General Public License).

5. Community and Collaboration: Open source promotes a culture of collaborative development. Developers and users often contribute to open source projects, improving the software, fixing bugs, and adding new features.

6. Transparency and security: Access to the source code provides total transparency about how the software works. This can lead to greater security, as problems are more easily identified and corrected by a large community.

Open source is as much a software development model as it is a philosophy. It focuses on practical collaboration and innovation, in contrast to free software’s emphasis on the ethical and moral freedoms of users. The terms “open source” and “free software” often overlap, but their underlying philosophies and approaches may differ slightly.

What are the fundamental differences and similarities between free software and open source software?

Free and open source software have many points in common, however and mainly in terms of philosophy, they can be distinguished.

The similarities:

1. Access to Source Code: Both allow access to the software’s source code, which is fundamental for modifying, studying and improving the software.

2. Modification and Redistribution Rights: Users may modify and redistribute the software, either in its original form or with modifications.

3. Community and Collaboration: Both encourage a collaborative approach to software development, involving contributions from diverse individuals and organisations.

4. Licences : Virtually all licences accepted by the open source community are also accepted by the free software community.

The differences :

1. Philosophy and objectives:
    – Free Software : Focuses on the ethical and moral freedoms of users. The Free Software Foundation (FSF) emphasises the user’s freedom to control the software and co-operate with the community. 
    – Open Source : Emphasises the practical benefits such as quality, flexibility and innovation of sharing source code. The Open Source Initiative (OSI) focuses less on ethical aspects and more on the development model.

2. Licensing criteria:
    – Free Software Licences: Must guarantee the four fundamental freedoms defined by the FSF.
    – Open Source Licences: Must comply with the OSI criteria, focusing on the practical accessibility of source code and its redistribution.

3. Community approach:
    – Free Software Community: Pays particular attention to users’ rights and ethical implications.
    – Open Source Community: Focuses more on collaborative development and the efficiency of the development process.

Although the terms “Free Software” and “Open Source” are often used interchangeably due to their many similarities, it is useful to recognise the differences that may exist in their philosophies. The choice between the two generally depends on the specific values and objectives of users and developers, although ultimately any ‘free’ licence is also ‘open source’ and vice versa.