The open source world has the BSD kernels in addition to the Linux kernel. There are also other open source operating systems based upon their own kernel, like

The open source world has the BSD kernels in addition to the Linux kernel. There are also other open source operating systems based upon their own kernel, like Haiku. Each kernel is backed by developers who have their own particular vision, just as each desktop environment is backed by developers with their own particular vision. I think this is a better comparison since only a few desktop environments are forks of other desktop environments, and most of the viable ones are forks of Gnome (much as most of the viable forks of kernels are forks of BSD).