The Minix 3.1.1 operating system is a simple and minimal Unix clone that is licensed under a BSD-like license.  It is designed to be a highly reliable, flexible, and secure operating system and is a work in progress.  It is nowhere near as mature as FreeBSD or Linux right now.  The OS has been designed and engineered to work in a Xen 2.0.7 domain.

To view a small animated presentation featuring a map of modifications made, check it out, here.

To download it and view other information about the project, go here.