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Why Microsoft Xenix has been closed and is not being developed? Or clone and make something like OpenIndiana to Solaris? I would like to play with this os already.

It was developed. It became SCO Open Server. We know what SCO became.

It's just a generic System V fork anyway, everyone and their dog had one back in the day, which is exactly why Microsoft abandoned it (They thought it was pointless to sell). Microsoft replaced it with Windows NT (and more specifically, the various Unix subsystems they've created and abandoned for it). Just play with FreeBSD, it's vaguely related to System V and it's an actual modern, networking OS.

Let's talk about Unix.

Unix was developed by Bell Labs, the research department of the Bell System, a collection of companies led by AT&T. The Bell System was effectively a monopoly in the United States on telecommunications. In 1949, the United States Department of Justice filed an antitrust suit against AT&T alleging that the company was using the Bell System's near-monopoly on telecommunications to unfairly branch into related fields such as the then-fledgling field of computer research and development. AT&T was allowed to continue existing but with a maximum 85% ownership of US telecommunications and a requirement to operate the Bell System in new fields on a non-commercial basis.

Flash forward to the mid-late 1970s.¹ AT&T has been (rightfully) targeted by another antitrust suit due to a continued monopoly and entrance into the computing field. Unix has been developed at Bell Labs. Sixth Edition Unix was licensed to educational institutions for free and commercial institutions for a modest licensing fee of $20,000. Seventh Edition followed in the late 70s, and was the final release of research Unix from Bell Labs. AT&T is still not allowed to sell Unix as a product.

They decide to do so anyways.

A number of companies purchase licenses to Seventh Edition Unix from AT&T, including Microsoft. Microsoft announces a plan to port Unix to the growing 16-bit microcomputer market. In January 1981, Microsoft Xenix arrives for Control Data Corporation's line of Zilog Z8001-based computers. By 1982, Xenix was ported to a non-IBM 8086 platform.

It is important to note here that Microsoft sold Xenix to OEMs, not end users. Companies like IBM and SCO would purchase Xenix, port it to their proprietary platforms, and ship it with their hardware.

In 1982, the Bell System was about to be broken up as a result of the antitrust suit. AT&T, now free of non-commercial obligations and still in ownership of Bell Labs, releases Unix System III, and a year later, Unix System V. Xenix, still based on Seventh Edition at this point, is ported to the IBM PC XT platform by SCO and released as SCO Xenix. SCO Xenix 3.0 is released in 1984 and is based on System III.

Microsoft, meanwhile, is continuing to develop MS-DOS for IBM PC compatibles. Multi-user support is explicitly not built into the DOS platform because of the success of Xenix at the time. The plan was to eventually converge Xenix and DOS into one platform. When the Bell System broke up, though, and AT&T was free to start selling System V, Microsoft pulled out of the Unix market to avoid competing with AT&T. Ownership of Xenix was transferred to SCO, and Microsoft began talks with IBM regarding a partnership to develop a new operating system for their upcoming PS/2 line of personal computers. This too was a project that Microsoft invested in, learned from, and sold off with greater ideas in mind, and in the late 1980s, development of Windows NT begun.²

SCO continued to develop Xenix for several years, eventually releasing a successor under the name SCO UNIX, then as SCO OpenServer. They acquired Novell's UnixWare operating system. In 1991, a hacker at the University of Helsinki wrote a toy Unix clone and released it as part of the growing free software movement. By the end of the decade, Microsoft internal memos said that the growth of the OS built around that hacker's Unix-like was a greater threat to SCO than Windows NT was. Microsoft moved on. SCO didn't.

Linux was on the rise in the server market, rapidly replacing aging and outdated proprietary Unix systems on proprietary big iron with a new, constantly-developed Unix-like on commercially available, off-the-shelf hardware.

SCO launched a campaign against Linux in 2003, alleging that their rights to Unix had been infringed and that there was System V code in the Linux system.³ They launched several lawsuits against companies aligned with Linux, including IBM, Red Hat, and Novell. Every single case was ruled in the defendants' favours. In 2007, the judge presiding over the SCO v. Novell case ruled that Novell was the owner of the rights to Unix.

Xenix is dead. It's not coming back. It is a relic of an era long gone. The Santa Cruz Operation is six feet under, and Microsoft doesn't care (nor should they). The OpenServer name brands an operating system based on FreeBSD. Xinuos owns it, and I don't think I've ever seen anyone use it.

Let Xenix rest.





Footnotes:

¹ My dates are most certainly a little bit off in this post. The eras are what are important here. Perhaps one day I'll expand it as a proper essay on the rise and fall of commercial Unix, but I'm sure someone else has already done a better job of it.

² Windows NT was a result of OS/2 development, but had a heritage in DEC's VMS operating system for the VAX and DEC Alpha platforms. Unix was a competitor to VMS on the VAX for a while, built out of Unix's long-standing existence on DEC's PDP-11 platform. Dave Cutler, one of the project leaders on VMS, was later the lead developer of Windows NT, and a prominent opponent of the Unix design.

³ The issue regarding the developers and lineage of System V Unix is multifaceted. Many licensees of System V contributed their code back into the core System V codebase, including Microsoft and SCO. SCO used their perceived ownership of the rights to Unix to allege that code originating in non-System V systems that was later ported into System V made these systems derivative works of System V.