Free software, also known as libre software and occasionally referred to as freedom-respecting software, is computer software that is distributed under terms that permit users to run the software for any purpose as well as to study, modify, and distribute it and any versions that have been adapted to their needs. Free software is an issue of liberty, not price; regardless of how much money is spent to get the programme, all users are legally free to do anything they choose with their own copies of free software, including making a profit from them. When it comes to software, a programme is considered "free" if it grants the end-users (as opposed to merely the creator) full authority over the software and, as a result, over the equipment they use to run it.
Users of a computer programme should have access to the program's source code, since this is the most efficient way to make modifications, if they are to have the legal right to investigate and alter the programme in question. Although this concept is frequently referred to as "access to source code" or "public availability," the Free Software Foundation (FSF) advises against thinking of it in those terms. Doing so may give the impression that users have an obligation (as opposed to a right) to provide non-users with a copy of the programme, which is contrary to the actual situation.
Richard Stallman is credited with tying the term "free software" to the sense in which it is currently being used and with starting the free software movement in 1983, when he launched the GNU Project. The GNU Project was a collaborative effort to create a freedom-respecting operating system, and it was also an effort to revive the spirit of cooperation that was once prevalent among hackers during the early days of the computer industry.