Q. Do typefaces or fonts used in a book or other document need to be credited? CMOS 4.106 makes me think they should, but maybe I misunderstood something.
A. That paragraph in CMOS is about crediting words and images borrowed from other sources and incorporated into your own work. Fonts* are in a different category. Any font licensed for public use that you’ve acquired legally can usually be used without credit.
This includes, for example, the fonts from Google Fonts, which can be downloaded for free and used in your publications or other documents without attribution (like Source Serif 4, the font used for the main text on this page); for details, see the Google Fonts FAQ page.
It also includes fonts acquired from Adobe, some of which are free (including the same Source Serif 4 family) and others of which require a Creative Cloud subscription or other type of purchase (see this page on font licensing from Adobe; there are some restrictions, but none of these involve giving credit to Adobe).
Not that you can’t give credit. Printed books often acknowledge fonts and their designers in a colophon, a brief statement (usually at the end) about details related to the book’s production. The one in CMOS can be found at the end of the printed book (and on the page that follows the entries for the letter z in the index at CMOS Online).
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* Traditionally speaking, a name like Garamond or Times refers to a typeface, whereas font refers to an assortment of characters for one of these typefaces in a specific size and style (e.g., italic). These days, the shorter word (font) is commonly used for both typeface and font.