​Can't speak for Alliant but Masscomp and DEC had shared authorship in he diagnostics group.  The former in C and later in BLISS of course; but the authors were pretty much the same.   If it works, don't mess with it.  Also the Tech's were all originally ex-DEC so it made sense - although the manufacturing guys were ex-DG.​

Actually there was a story I tell.   Both Masscomp and DEC were using the same HW CAD system at one point.   DEC has a microcode assembler that had originally been written in PDP-11 assembler and was running compatibility mode on the Vax.   Masscomp wrote a new microcode assembler that was "frighteningly similar"  in C that tjt the UNIX guys put together with lex/yacc and the like one weekend for the HW team.   Knowledge of this made its way to the mill.   It was also know that  DEC has a number of CAD libraries that the HW guys had been using to make their board layouts easier -- discussions occurred over beers at the Mau Kaui...  tapes some how fell out of cars one night... and DEC had a microcode assembler running on Ultrix in C and somehow our HW guys stopped complain about some missing libraries they wanted.

Clem