don't trust any texts that aren't open source themselves. anything by Richard Stallman is a good start:

free software philosophy (think of “free” as in “free speech,” not as in “free beer”)
https://www.gnu.org/philosophy/free-sw.en.html

GNU manifesto
http://www.gnu.org/gnu/manifesto.en.html

>>46246
First of all there are two concepts of free, "gratis" and "libre", see: https://en.wikipedia.org/wiki/Gratis_versus_libre

As for "free software", the term got hijacked by Stallman (aka RMS), and is commonly used by him and his sympathizers to mean "libre software", but people who are either unaware or don't care for his particular definition may use the term to refer to software that is gratis. People who don't want to cause confusion may avoid the term altogether, and look for specific alternatives, like literally using "gratis" or "libre", or other terms like "open-source software".