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

dusty deck
 n.

    Old software (especially applications) which one is obliged to remain
    compatible with, or to maintain (DP types call this legacy code, a term
    hackers consider smarmy and excessively reverent). The term implies that
    the software in question is a holdover from card-punch days. Used esp. when
    referring to old scientific and number-crunching software, much of which
    was written in FORTRAN and very poorly documented but is believed to be too
    expensive to replace. See fossil; compare crawling horror.


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

dusty deck

   Old software (especially applications) which one is obliged to
   remain compatible with, or to maintain.  DP types call this
   "legacy code", a term hackers consider smarmy and excessively
   reverent.  The term implies that the software in question is a
   holdover from card-punch days.  Used especially when referring
   to old scientific and number crunching software, much of
   which was written in Fortran and very poorly documented but is
   believed to be too expensive to replace.  See fossil;
   compare crawling horror.

   [Jargon File]