PDFkit seems to be a name a few different things in stuff like node and ruby. I think the Apple PDFkit is probably just wrapping Apple’s in house PDF tech that Preview uses?
It does not seem to have any requirements than JS - browser or Node. There is an online demo that works with Firefox on Linux so not wrapping anything else.
the pdfkit from the first google result doesn't seem to be related to apple's. what happened here is that "pdfkit" is a very generic name (that will tend to show up because people love writing pdf-related software) that also happens to coincide with apple's convention of naming their frameworks something-kit (uikit, appkit, avkit, ...)
I just tried a few PDFs in Chromium and PDFium seems to be much better than pdf.js - faster and handles forms more smoothly.