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

UN*X
 n.

    Used to refer to the Unix operating system (a trademark of AT&T, then of
    Novell, then of Unix Systems Laboratories, then of the Open Group; the
    source code parted company with it after Novell and was owned by SCO, which
    was acquired by Caldera) in writing, but avoiding the need for the ugly ?
    typography (see also (TM)). Also used to refer to any or all varieties of
    Unixoid operating systems. Ironically, lawyers now say that the requirement
    for the trademark postfix has no legal force, but the asterisk usage is
    entrenched anyhow. It has been suggested that there may be a psychological
    connection to practice in certain religions (especially Judaism) in which
    the name of the deity is never written out in full, e.g., ?YHWH? or ?G--d?
    is used. See also glob and splat out.


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

UN*X

    A way of writing the
   operating system name "Unix" that avoided the (TM) postfix
   that was believed to be a legal requirement in the days when
   Unix was a trademark of AT&T.

   It has been suggested that there may be a psychological
   connection to practice in certain religions (especially
   Judaism) in which the name of the deity is never written out
   in full, e.g. "YHWH" or "G--d" is used.

   See also glob.

   (1998-04-17)