I was recently asked why nobody tries to make money off of Linux, given that it's better than Windows. Often, the question is asked differently: how can such a good operating system be free? It's actually a complicated subject, but here's my effort to summarize how and why Linux is free.
Companion Article: http://nerdonthestreet.com/tech/?p=51
Sources:
http://www.tuxradar.com/newtolinux
http://www.gnu.org/copyleft/gpl.html
http://www.linux.com/news/featured-blogs/200-libby-clark/744744-10-best-quotes-from-linus-torvalds-keynote-at-linuxcon-europe
http://www.linfo.org/linus.html