Open Source is not a fantasy or a marginal practice. Very large, and very important software development projects have resulted from an open source process of production. The best known are Linux and Apache, but there are many others, and this is an expanding practice in the research world, in the hackers world, in the education world, in the institutional world and in the business world, including some large corporations, such as IBM. As of 2004, Linux is the operating system for more than a third of active web servers in the world, and it is the operating system for about 14% of the large server market. Apache largely dominates the web server market – with 65% of all active web sites running Apache. Sendmail, and many other popular programs, are also produced and distributed as Open Source. Open source introduces a new, cooperative form of production that transcends the traditional limits of the social division of labor built on hierarchies. Indeed, open source works as an open network of voluntary cooperation.