4.3BSD_Net/2 was released June 1991 and was an almost clean1? version of 4.3BSD. Six month later the six remaning kernel-files were rewritten by Bill Jolitz who released the fully compileble system on FTP. Unfortunally Bill Jolitz didn't have the time to continue the development of what now was called 386BSD so the development was taken over by another group of developers who called their version NetBSD.
1? Clean as in not including code from 32/V.
See also CategoryOperatingSystem
6 pages link to 4.3BSD_Net/2: