Let that sink in. How many developers and admins rely on readline for their daily work? How many critical installations world wide depend on it?
As a contrast: How much revenue is generated with, and how many people work on, something as mundane as a chat application for mobile phones?
Sometimes it is astonishing that our software eco system actually works.
One reason we get so much bang-for-the-buck with software is that the maintenance costs for a given software package aren't necessarily proportional to the number of places/times it gets used.
Not... That... Big? It is a _huge_ library. A naive wc -l of just the c files, and none of the headers, lists a result of 30,654.
That's not a small project. And as it's a library and not a self-contained application, that's one of the bigger libraries around. In fact that's one of the sighted inspirations for linenoise, that readline is too big.