wkhtmltopdf repository has been archived on GitHub. Maybe if you're lucky, someone will make a fork, but it's quite hard for a fork to get traction and retain some user base / not to be immediately discarded as well.

Qt WebKit is, compared to Chromium, quite light-weight at 30-40MB. However it's still quite large, compared to say MigraDoc + PDFsharp at 1MB. Truthfully, if there was a well maintained project using it, I'd have actually considered it.

Though Qt WebKit also moves you into the murky water of copy-left licensing, as Qt is released under LGPL. With the setup of using a shared native library, this should work, but might still not be something everyone wants to touch.

wkhtmltopdf is unmaintained and deprecated though.