Linux is an open source operating system originally designed for the 386 computer(and more recent x86s) by Linus Torvalds and has since been released for many types of computers, such as the Mac, PowerPC, SPARC stations and others. It runs well on older computers, has excellent networking capabilities, and a very cute penguin mascot, Tux. The GNU General Public Liscense describes the Copyright which actually is designed to give rights, as opposed to taking them away from the user(often referred to as a copy-left).
Linux is part of the free software movement, which provides a viable alternative to the corporate paradigm. It is designed and improved by people all over the world, who share their knowledge and programming skills to contribute to a better product. Because it is designed well, it has the ability to run on older computers, many of which are becoming waste products. Anything that can potentially reduce consumerism in the computer industry would be a great boon to the environmental health of the world.
http://www.trinux.org, http://www.gnu.org, http://www.opensource.org, http://www.openclassroom.org