Since 2005, more than 3700 individual developers have contributed their time towards modifications of the Linux kernel operating system. A recent report here shows exactly how far and how fast that project has come, and the extent that Linux has become the province of corporations such as IBM, Novell, Red Hat and others. Since 2005, the community of developers has actually doubled, but new releases continue to appear every 100 days or so,. This is quite the opposite of major OS projects that are under the control of a single (or smaller number of) company such as Windows, OS/2, and DOS. Here is the chart from the study that shows the breakdown by company affiliation. None means the collection of individual developers who have volunteered their time, while unknown could be a corporate sponsor or an individual.