kpathsea is a basic library that anyone who has tweaked TeX configurations would know about. It has a certain syntax for subdirectory searching that you have to learn, as well as a utility command (kpsewhich) that you run quite a lot to debug "file-not-found" problems.
Knuth's Web literate programming system is based on transforming the literate sources two different ways: "weave" transforms the source into the published book form, and "tangle" strips all comments, and massively rearranges the source into compilable Pascal (Rearranging was probably a somewhat Pascal specific feature, and newer literate programming systems don't necessarily rearrange anymore, I think).
Since their C code is based on the tangled code, their transformation discards the ENTIRE comments of the original source (and simply not stripping the comments would not help, because in the rearranged order they wouldn't make much sense anymore). Essentially, they are rendering TeX illiterate.
I can't conceive how this could possibly lead to a more maintainable product. TeX has a perfectly workable way of making arbitrary local changes through "Changefiles". The Pascal/C code was never meant to be edited directly.