This article is from the Apple II GNO FAQ, by Devin Reade with numerous contributions by others.
A#2.1: GNO contains components that originate with a variety of
flavors of UNIX. These include 4.3BSD, XINU, and SYSV.
It is mostly BSD. As of GNO v2.0.6, GNO has become closer
to 4.4BSD. Work is in progress to make it as compliant as
possible to POSIX 1003.1 and POSIX 1003.2.
 
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