From the Wall Street Journal: "Software connected with the FreeBSD open-source operating system
is used in several places deep inside several versions of Microsoft's
Windows software, such as in the "TCP/IP" section that arranges all
connections to the Internet. The company also uses FreeBSD on
numerous "server" computers that manage major functions at its
Hotmail free e-mail service, whose registered users exceed 100
million and make it one of the Web's busiest sites."
June 18, 2001