William N. Joy (born 1954), commonly known as Bill Joy, co-founded Sun Microsystems in 1982 along with Vinod Khosla, Scott McNealy and Andy Bechtolsheim, and served as chief scientist at the company until 2003.
Bill Joy was the person largely responsible for the authorship of Berkeley UNIX, also known as BSD, from which spring many modern forms of UNIX, including FreeBSD, NetBSD, and OpenBSD. Some of his most notable contributions were TCP/IP, the vi editor, NFS, and the csh shell.
In the early 1980s, DARPA had contracted BBN to add TCP/IP, devised by Vinton Cerf and Bob Kahn, into Berkeley UNIX. Joy had been instructed to plug BBN's stack into Berkeley Unix. But Joy refused to do so. In his opinion, BBN's TCP/IP wasn't good enough. So he wrote his own high-performance TCP/IP stack.
As John Gage tells it, "BBN had a big contract to implement TCP/IP, but their stuff didn't work, and Joy's grad student stuff worked. So they had this big meeting and this grad student in a T-shirt shows up, and they said, 'How did you do this?' And Bill said, 'It's very simple -- you read the protocol and write the code.'" Others dispute this version of events.
In 2000 he gained notoriety with the publication of his article in Wired Magazine, "Why the future doesn't need us", in which he put forward, in what some have described as a "neo-Luddite" position, that he was convinced by the growing advances in genetic engineering and nanotechnology that intelligent robots would replace humanity, at the very least in intellectual and societal dominance, in the relatively near future.
Bill Joy once said, "My method is to look at something that seems like a good idea and assume it's true." 
- BSD Unix: Power to the people, from the code - Salon article
- Why the future doesn't need us, Wired, April 2000
- Bill Joy's Hi-Tech Warning
- Bill Joy, techcast.ddj.com
- Co-founder Joy to leave Sun, news.com, September 9, 2003
- Joy After Sun, interview with Brent Schlender for Fortune, September 29, 2003
- Hope Is a Lousy Defense., interview with Spencer Reiss for Wired, December 2003
- Internet archive of biography from Sun Microsystems in 2003
- CNet Interview: Talking tech with Bill Joy - 31 March 2005
- NerdTV interview (video, audio, and transcript available) - 30 June 2005