The primary author of Linux is Linus Torvalds. Since his original versions, it has been improved by countless numbers of people. It is a clone, written entirely from scratch, of the Unix operating system. One of the more interesting facts about Linux is that its development occurs simultaneously around the world.
Linux has been copyrighted under the terms of the GNU General Public License (GPL). This is a license written by the Free Software Foundation (FSF) that is designed to prevent people from restricting the distribution of software. In brief, it says that although money can be charged for a copy, the person who received the copy can not be prevented from giving it away for free. It also means that the source code must be available. This is useful for programmers. Anybody can modify Linux and even distribute his/her modifications, provided that they keep the code under the same copyright.
Why work on Linux? Linux is generally cheaper (or at least no more expensive) than other operating systems and is frequently less problematic than many commercial systems. But what makes Linux different is not its price (after all, why would anyone want an OS - even a free one - if it is not good enough?) but its outstanding capabilities: