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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