There are a number of Unix-like operating systems under active development, descended from the Berkeley Software Distribution (BSD) series of UNIX variants developed (originally by Bill Joy) at the University of California, Berkeley, Department of Electrical Engineering and Computer Science.
FreeBSD is a free Unix-like operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD).
NetBSD is a freely redistributable, open source version of the Unix-derivative Berkeley Software Distribution (BSD) computer operating system.
It was the second open source BSD descendant to be formally released, after 386BSD, and continues to be actively developed.
A 32-bit version for the VAX platform was released as 3BSD, and the 4.xBSD series added many new features, including TCP/IP networking.