There's nothing really stopping anyone from implementing the human interface guidelines into a UI library. I wonder what's keeping people from building one.

I suck at front end design, but I personally would pay money for a Bootstrap-type setup based on Apple HIG. In my (admittedly biased) opinion, Apple Human Interface Guidelines seem like common sense. I am speaking from the perspective of someone who has a web application that has “normal” people as their primary user and thus have spent countless hours providing support for simple things that might seem obvious to the more technically literate. Let’s not insult users, but let’s not assume they’re all web natives either.