386BSD is the mother off The Three (free) BSDs today. 386BSD was based on the 4.3BSD_Net/2 tapes. Due to the BSD licence problems in early 90s' development halted quite quick after it's initial release July 14 1992.
386BSD resulted into (directly or indirectly) BSD/386, NetBSD, FreeBSD, BSD/OS, Darwin, OpenBSD and more.
See also CategoryOperatingSystem