Free software and operating systems provide freedoms that proprietary systems do not.
According to the GNU Free Software Philosophy, a program is free software if the users have the four essential freedoms.
Freedom 0: The freedom to run the program as desired, for any purpose.
Freedom 1: The freedom to study how the program works, and change it to do what you want. Access to the source code is a necessary condition for this.
Freedom 2: The freedom to redistribute copies to help others.
Freedom 3: The freedom to distribute copies of your modified versions to third parties. This allows you to offer the entire community the opportunity to benefit from the modifications. Access to the source code is a necessary condition for this.
Note: “The reason they are numbered 0, 1, 2 and 3 is historical. In 1990 there were three freedoms, numbered 1, 2 and 3. Then we realized that the freedom to run the program had to be mentioned in a way explicit. It was clearly more basic than the other three, so it should precede them. Instead of renumbering the others, we designated it as freedom 0.”
Licenses for proprietary operating systems go against the four freedoms that free software offers.
If you use macOS®, you must accept the Apple Software License Agreement.
If Windows® was pre-installed at the factory on your computer, you must accept the Microsoft Software License Terms – Windows Operating System (OEM) to use it.
If you purchased Windows®, you must accept the Microsoft Software License Terms – Windows Operating System (Retail) to use it.
Only GNU is Free Software
Only Free Software, based on the GNU Operating System (GNU’s Not Unix) guarantees your freedoms.
Software must be distributed under one of the Free Licenses to be considered free.
The GNU/Linux-libre distributions are the only ones that completely respect the four essential freedoms of the users. Trisquel GNU/Linux is a user-friendly distribution of the GNU Operating System, with the Linux-libre Kernel.