Editing MVS (section)

==Closely related operating systems==
{{Further|jp:VOS3}}
Japanese mainframe manufacturers [[Fujitsu]] and [[Hitachi]] both repeatedly and illegally obtained IBM's MVS [[source code]] and internal documentation in one of the 20th century's most famous cases of [[industrial espionage]].<ref name=FAS.cong>https://fas.org/irp/congress/1989_cr/h890712-japan.htm An hour's worth of "minutes" from a Congressional Hearing about Japanese Industrial Espionage against IBM</ref> Fujitsu relied heavily on IBM's code in its [[Fujitsu MSP|MSP]] mainframe operating system, and likewise Hitachi did the same for its VOS3 operating system. MSP and VOS3 were heavily marketed in Japan, where they still hold a substantial share of the mainframe installed base, but also to some degree in other countries, notably Australia. Even IBM's bugs and documentation misspellings were faithfully copied. IBM cooperated with the U.S. [[Federal Bureau of Investigation]] in a [[sting operation]], reluctantly supplying Fujitsu and Hitachi with proprietary MVS and mainframe hardware technologies during the course of multi-year investigations culminating in the early 1980s—investigations which implicated senior company managers and even some Japanese government officials. [[Amdahl Corporation|Amdahl]], however, was not involved in Fujitsu's theft of IBM's [[intellectual property]]. Any communications from Amdahl to Fujitsu were through "Amdahl Only Specifications" which were scrupulously cleansed of any IBM IP or any references to IBM's IP.

Subsequent to the investigations, IBM reached multimillion-dollar settlements with both Fujitsu and Hitachi, collecting substantial fractions of both companies' profits for many years. Reliable reports indicate that the settlements exceeded US$500,000,000.<ref>{{Cite web |last=Lazzareschi |first=Carla |date=1988-11-30 |title=Fujitsu Payments to IBM Could Surpass $1 Billion |url=https://www.latimes.com/archives/la-xpm-1988-11-30-fi-534-story.html |access-date=2025-02-04 |website=Los Angeles Times |language=en-US}}</ref><ref name=FAS.cong/><ref group="NB">the Congressional testimony, near the end, only says "Hitachi has yet to admit that any of IBM's secrets were used in the development of new products, and they have not yet compensated IBM for the huge expenses involved in settling the case."</ref>

The three companies have long since amicably agreed to many joint business ventures. For example, in 2000 IBM and Hitachi collaborated on developing the IBM z900 mainframe model.

Because of this historical copying, MSP and VOS3 are properly classified as [[Fork (software development)|"forks"]] of MVS, and many third-party software vendors with MVS-compatible products were able to produce MSP- and VOS3-compatible versions with little or no modification.<ref>{{cite magazine| url=http://www.time.com/time/magazine/article/0,9171,925515,00.html | archive-url=https://web.archive.org/web/20101015065706/http://www.time.com/time/magazine/article/0,9171,925515,00.html | archive-date=15 October 2010 | url-status=dead | magazine=Time | first1=Charles | last1=Alexander | first2=Bob | last2=Buderi | title=Now, from the FBI: Japanscam | date=5 July 1982}}</ref><ref>{{cite news| url=https://www.nytimes.com/1983/05/16/business/hitachi-fbi-tapes-are-released.html | work=The New York Times | first=Michael S. | last=Malone | title=Hitachi-F.B.I. Tapes Are Released | date=16 May 1983}}</ref><ref>{{Cite book |first=Marie |last=Anchordoguy |title=Reprogramming Japan: The High Tech Crisis Under Communitarian Capitalism |publisher=Cornell University Press |year=2005 |page=159}}</ref>

When IBM introduced its 64-bit [[z/Architecture]] mainframes in the year 2000, IBM also introduced the 64-bit z/OS operating system, the direct successor to OS/390 and MVS. Fujitsu and Hitachi opted not to license IBM's z/Architecture for their quasi-MVS operating systems and hardware systems, and so MSP and VOS3, while still nominally supported by their vendors, maintain most of MVS's 1980s architectural limitations to the present day. Since z/OS still supports MVS-era applications and technologies— z/OS still contains most of MVS's code, albeit greatly enhanced and improved over decades of evolution—applications (and operational procedures) running on MSP and VOS3 can move to z/OS much more easily than to other operating systems.