Question

What is free software and its three characteristics

Answer 1

Free software is software that can be freely used, modified, and redistributed with only one restriction: any redistributed version of the software must be distributed with the original terms of free use, modification, and distribution (known as copyleft). The definition of free software is stipulated as part of the GNU Project and by the Free Software Foundation. Free software may may be packaged and distributed for a fee; the "free" refers to the ability to reuse it, modified or unmodified, as part of another software package. As part of the ability to modify, users of free software may also have access to and study the source code.

Any software can be Free. GNU/Linux, Apache, Gcc, Perl. Examples for system related software.

The actual product is gratis. However: Price plays a role, but is not crucial.

Source code is available. Important for the most of the following four rights, which every user of Free Software has. Software may be used for any purpose