Definition of Free and Open Source Software

In 1985, the GNU project founded by Richard Stallman (also founder of Free Software Foundation), along with his four freedoms referenced the concept of free software. The goal was to make a free OS compatible with Unix. This started a real social movement of free software.

Free refers to “free speech” rather than cost

Four Essential Freedoms by Richard Stallman

1. “The freedom to run the program as you wish, for any purpose.”
2. “The freedom to study how the program works, and change it so it does your computing as you wish. Access to the source code is a precondition for this.”
3. “The freedom to redistribute copies so you can help others.”
4. “The freedom to distribute copies of your modified versions to others. By doing this you can give the whole community a chance to benefit from your changes. Access to the source code is a precondition of this.”

The concepts stress on the importance of free software for modification and distribution.

This is the idea of allowing development branches or forks to spin off from the original software.

While coined in 1998, open source heightened with Linux’s (GNU is not Unix) popularity and a pragmatic approach came way during software development. Although it was foundationally started by the four essential freedoms.

Note: While people consistently refer to the OS as Linux, Linux is technically the kernel with GNU and other software packaged to be a specific distribution.

Open Source and Free Software may sound like peanut butter and jelly, but they often end up conflicting.

Open Source concepts due to restrictions on disclosure, change, or connection with other software components prevent it from adhering to all four freedoms

This is why software licenses were created as they are available to assist users in determining their use, distribution, and modification.

(https://www.tcpipacademy.com/open-source-licensing/)