from where does he draw the idea "code-script"? Is it from the developing information theory of the time? Somewhere else?

There is definitely the idea of a code running in the sense of programming, which was likely not a common conceptualization at the time.

On p. 22 he uses the phrase "law-code" which is likely the closer meaning of code he's using and not the sense of genetic code as understood much later when DNA and the underlying protein coding sequences were unraveled.

Morse code may also be a tangential underlying meaning of his sense of "code" as something unknown but potentially revealable.

Watts, Charles J. The Cost of Production. Muskegon, MI: The Shaw-Walker Company, 1902. http://archive.org/details/costproduction01wattgoog.

Short book on managing manufacturing costs. Not too much of an advertisement for Shaw-Walker manufactured goods (files, file management, filing cabinets, etc.). Only 64 pages are the primary content and the balance (about half) are advertisements.

Given the publication date of 1902, this would have preceded the publication of System Magazine which began in 1903. This may have then been a prototype version of an early business magazine, but with a single author, no real editorial, and only one article.

Presumably it may also have served the marketing interests of Shaw-Walker as a marketing piece as well.

Tangentially, I'm a bit intrigued by the "Mr. Morse" mentioned on page 109 who is being touted as an in-house consultant for Shaw-Walker.... Is this the same Frank Morse who broke off to form the Browne-Morse Co.? (very likely)

see: see also: https://hypothes.is/a/Sp8s4sprEe24jitvkjkxzA for a snippet on Frank Morse.

Morse theory can be used to study critical points.