The Free On-line Dictionary of Computing (19 January 2023):

(TM)

    (Trademark) An ASCII rendition of the trademark
   superscript symbol, appended to phrases that the author feels
   should be recorded for posterity.

   It is often used ironically as a form of protest against software
   patents, algorithm patents and "look and feel" lawsuits.

   [Jargon File]

   (2014-11-27)


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

(TM)
 //

    [Usenet] ASCII rendition of the ™ appended to phrases that the author feels
    should be recorded for posterity, perhaps in future editions of this
    lexicon. Sometimes used ironically as a form of protest against the recent
    spate of software and algorithm patents and look and feel lawsuits. See
    also UN*X.