Ancient UNIX

{{Short description|Early releases of Unix operating system}}{{Merge to|Research Unix|date=December 2024}}File:Version 5 Unix SIMH PDP11 Emulation.png for the PDP-11, running on SIMH]]

File:Version 6 Unix SIMH PDP11 Emulation KEN.png for the PDP-11, running in SIMH]]

File:Version 7 Unix SIMH PDP11 Emulation DMR.png for the PDP-11, running in SIMH]]

Ancient UNIX is any early release of the Unix code base prior to Unix System III, particularly the Research Unix releases prior to and including Version 7 (the base for UNIX/32V as well as later developments of AT&T Unix).

After the publication of the Lions' book, work was undertaken to release earlier versions of the codebase. SCO first released the code under a limited educational license.{{Citation needed|date=October 2009}}

Later, in January 2002, Caldera International (later to become SCO Group and made defunct) relicensed (but has not made available) several versions under the four-clause BSD license, namely:{{cite web |url=http://www.lemis.com/grog/UNIX/|title=Liberal license for ancient UNIX sources|last=Johnson II |first=Dion L. |date=2002-01-24}}{{cite web|url=http://www.tuhs.org/Archive/Caldera-license.pdf|archive-url=https://web.archive.org/web/20090219220353/http://www.tuhs.org/Archive/Caldera-license.pdf|archive-date=February 19, 2009|title=Dear Unix enthusiasts|last=Broderick|first=Bill|date=January 23, 2002|publisher=Caldera International}}

• Research Unix: (early versions only)
• Version 1 Unix
• Version 2 Unix
• Version 3 Unix
• Version 4 Unix
• Version 5 Unix
• Version 6 Unix
• Version 7 Unix
• UNIX/32V

{{As of|2022}}, there has been no widespread use of the code, but it can be used on emulator systems, and Version 5 Unix runs on the Nintendo Game Boy Advance using the SIMH PDP-11 emulator.{{cite web |url=http://www.kernelthread.com/publications/gbaunix/ |title=UNIX® on the Game Boy Advance |last=Singh |first=Amit |date=August 2004 |access-date=2009-10-22 |archive-date=2006-08-31 |archive-url=https://web.archive.org/web/20060831141959/http://www.kernelthread.com/publications/gbaunix/ |url-status=dead }} Version 6 Unix provides the basis for the MIT xv6 teaching system, which is an update of that version to ANSI C and the x86 or RISC-V platform.

The BSD vi text editor is based on code from the ed line editor in those early Unixes. Therefore, "traditional" vi could not be distributed freely, and various work-alikes (such as nvi) were created. Now that the original code is no longer encumbered, the "traditional" vi has been adapted for modern Unix-like operating systems.{{cite web |url=http://ex-vi.sourceforge.net/ |title=The Traditional Vi}}

SCO Group, Inc. was previously called Caldera International. As a result of the SCO Group, Inc. v. Novell, Inc. case, Novell, Inc. was found to not have transferred the copyrights of UNIX to SCO Group, Inc.{{cite web|url=http://www.groklaw.net/pdf3/SCOvNovell10-4122.pdf|title=10th Circuit Court of Appeals Decision}} Concerns have been raised regarding the validity of the Caldera license.{{cite web|url=https://wiki.tuhs.org//doku.php?id=events:free_licenses|title=The Push to Get Free Unix Licenses|author=Warren Toomey}}{{cite web|url=https://virtuallyfun.com/wordpress/2018/11/26/why-bsd-os-is-the-best-candidate-for-being-the-only-tested-legally-open-unix/|title=Why BSD/OS is the best candidate for being the only tested legally open UNIX.}}