The Collaborative International Dictionary of English v.0.48:

Its \Its\ ([i^]ts), poss. pron.
   Possessive form of the pronoun it. See It.
   [1913 Webster]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

ITS
       Incompatible Time-sharing System (DEC)


V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

ITS
       International Telecommunications Society (org.)


The Jargon File (version 4.4.7, 29 Dec 2003):

ITS
 /I?T?S/, n.

    1. Incompatible Time-sharing System, an influential though highly
    idiosyncratic operating system written for PDP-6s and PDP-10s at MIT and
    long used at the MIT AI Lab. Much AI-hacker jargon derives from ITS
    folklore, and to have been ?an ITS hacker? qualifies one instantly as an
    old-timer of the most venerable sort. ITS pioneered many important
    innovations, including transparent file sharing between machines and
    terminal-independent I/O. After about 1982, most actual work was shifted to
    newer machines, with the remaining ITS boxes run essentially as a hobby and
    service to the hacker community. The shutdown of the lab's last ITS machine
    in May 1990 marked the end of an era and sent old-time hackers into
    mourning nationwide (see high moby). There is an ITS home page.

    2. A mythical image of operating-system perfection worshiped by a bizarre,
    fervent retro-cult of old-time hackers and ex-users (see troglodyte,
    sense 2). ITS worshipers manage somehow to continue believing that an OS
    maintained by assembly-language hand-hacking that supported only monocase
    6-character filenames in one directory per account remains superior to
    today's state of commercial art (their venom against Unix is particularly
    intense). See also holy wars, Weenix.


The Free On-line Dictionary of Computing (30 December 2018):

ITS

   1. Incompatible time-sharing System

   An influential but highly idiosyncratic operating system
   written for the PDP-6 and PDP-10 at MIT and long used at
   the MIT AI Lab.  Much AI-hacker jargon derives from ITS
   folklore, and to have been "an ITS hacker" qualifies one
   instantly as an old-timer of the most venerable sort.  ITS
   pioneered many important innovations, including transparent
   file sharing between machines and terminal-independent I/O.
   After about 1982, most actual work was shifted to newer
   machines, with the remaining ITS boxes run essentially as a
   hobby and service to the hacker community.  The shutdown of
   the lab's last ITS machine in May 1990 marked the end of an
   era and sent old-time hackers into mourning nationwide (see
   high moby).  The Royal Institute of Technology in Sweden is
   maintaining one "live" ITS site at its computer museum (right
   next to the only TOPS-10 system still on the Internet), so
   ITS is still alleged to hold the record for OS in longest
   continuous use (however, WAITS is a credible rival for this
   palm).

   2. A mythical image of operating system perfection worshiped
   by a bizarre, fervent retro-cult of old-time hackers and
   ex-users (see troglodyte).  ITS worshipers manage somehow to
   continue believing that an OS maintained by assembly
   language hand-hacking that supported only monocase
   6-character filenames in one directory per account remains
   superior to today's state of commercial art (their venom
   against Unix is particularly intense).

   See also holy wars, Weenix.

   [Jargon File]

   (1994-12-15)