(taken from gunkies.org and other sources.)
4.3BSD-UWisc is a modified version of 4.3BSD made at the University of Wisconsin. Its main claim to fame is that it was the first 4BSD to incorporate the NFS code from SunOS.
The files here come from the UWisc4.3 area of the Unix Archive, and were probably donated by James Lothian.
For more information about 4.3BSD, see Twenty Years of Berkeley Unix by Kirk McKusick.