Как я понимаю, этот комментарий не относится к реализации под 8086/8088, а остался (с добавлением слова "ORIGINALLY"?) от одного из их предыдущих Бейсиков под другой процессор (8080?), который потом кто-то (не упомянутый?) вольно переводил на ассемблер 8086/8088 (по-видимому уже не используя исходную систему макросов для MACRO-10).

Вот подробнее о том как на PDP-10 делались Бейсики под 8080, 6800, 6502: https://www.pagetable.com/?p=774

The source of the 8080 version states:

PAUL ALLEN WROTE THE NON-RUNTIME STUFF.
BILL GATES WROTE THE RUNTIME STUFF.
MONTE DAVIDOFF WROTE THE MATH PACKAGE.

People have since wondered what runtime vs. non-runtime meant, especially since Paul Allen’s recent debate on whether the company’s ownership was faily split.

The BASIC for 6502 source sheds some light on this:

NON-RUNTIME STUFF
        THE CODE TO INPUT A LINE, CRUNCH IT, GIVE ERRORS,
        FIND A SPECIFIC LINE IN THE PROGRAM,
        PERFORM A "NEW", "CLEAR", AND "LIST" ARE
        ALL IN THIS AREA. [...]

So by “runtime” they just literally mean “at run time”: all code that is active when the program runs, as opposed to non-runtime, which is all code that assists editing the program.

By this understanding, we can assume this:

    Paul Allen wrote the macro package for the MACRO-10 assembler, the 6502 simulator, the tokenizer, the detokenizer, as well as finding, inserting and deleting BASIC lines.
    Bill Gates implemented all BASIC statements, functions, operators, expression evaluation, stack management for FOR and GOSUB, the memory manager, as well as the array and string library.
    Monte Davidoff wrote the floating point math package.

Еще куча подробностей: https://www.pagetable.com/?cat=27

И немного шуток: https://www.pagetable.com/?p=43

Другой источник: http://altairbasic.org/other%20versions/ian.htm

00410  COPYRIGHT 1975 BY BILL GATES AND PAUL ALLEN
00420  -------------------------------------------

It also says 'written originally on the PDP-10 at Harvard from February 9 to April 27.' Remember that the spooler output (above) showed that this printout was made on 30th April 1975.