NavList:

Hi,

>Does anyone recognize the output style of this data, with some degree of certainty, from another USNO software package?

Agreed, it appears to be same output as the old USNO Floppy Almanac and ICE programs.

>I have not found the source code for ICE online

Unlikely, the "source code" is owned by the Astronomical Applications Department of the U.S. Naval Observatory; FYI the source code was entirely written in ANSI standard Fortran 77.
https://aa.usno.navy.mil/index.php

In the fall of 1986 the annual Floppy Almanac was released; around the same time a version of the Floppy Almanac that provided data for extended periods of time—the Interactive Computer Ephemeris (ICE)—was also developed but not publicly released.  The FA and ICE source codes were entirely written in Fortran 77.  The Floppy Almanac was superseded in 1993 by Version 1.0 of MICA, the Multiyear Interactive Computer Almanac for MS-DOS and Apple Macintosh systems.  My assumption is that the original Fortran 77 code that was used on the Floppy Almanac's and on ICE v.50 and ICE v.51 was also used on the first version of MICA for DOS-based PCs and possibly is still in use today.

>and I don't know if it could be decompiled or modified to update its Delta-T values.

Again, the code is owned by the USNO so I will leave it up to them to answer this question:

Astronomical Applications Department
U.S. Naval Observatory
3450 Massachusetts Avenue NW
Washington, DC 20392-5420 USA
Phone: 1 (202) 762-1617
DSN: 762-1617
Fax: 762-1612
E-mail: navobsy_aa-help@navy.dot.mil

or you could reach out to the original (now retired) programmer:

George H. Kaplan, Ph.D. Astronomer
35 Oak Street
Colora, MD   21917 USA
Phone:  1-410-658-0484
E-mail: gk@gkaplan.us
http://gkaplan.us/

>because I like DOS

Me too; I still run ICE v.51, SkyGlobe v3.6, etc. on my HP 200LX a DOS based palmtop which tucks in nicely with my Celesticomp V, Sextant, watch, etc.

--
Ian Gifford 42° 38’ N, 71° 24’ W