NetBSD took its roots from the original UCB 4.3BSD via the Networking/2 release and 386BSD. Since then, in addition to the many developers within the project, it has imported changes from many other sources, including 4.4BSD Lite. NetBSD has also been used as the basis of other derivatives, including the University of Utah's Lites (on top of Mach), and the FreeBSD 1.x line.
Additional modifications to NetBSD 1.3.X port to RTOS/embedded environment performed by PSO Systems Inc.