Blink the web engine Chromium is using is a fork of the WebCore component of WebKit,which was originally a fork of the KHTML and KJS libraries from KDE. So it is other way around. You are right I the sense that the biggest contributor to WebKit is Google.

It is still updated judging by the git commits. Btw Konqueror gets new releases as well.

For KDE development I would recommend the KDE Neon developer edition as it has all the tools you need to get started.

I did witness the transaction from 3.5 to 4 and from 4 to 5. Yet I am super excited about 6.