I'd say Apple falls into that category (although they don't solely depend on their browser, it is a major part of their ecosystem) - the day they stop maintaining Safari and just ship Chrome (or a skinned Chromium) on iOS and macOS is the day I stop using the Apple ecosystem.
To be fair, Apple has (or had on the 10th of June) a market cap of 1.5T and they maintain Safari and Webkit (which GOOG forked to create Blink).
- Apple has Safari which uses Webkit (which was forked from KHTML as you noted)
- Mozilla has Firefox which uses Gecko (originally from Netscape)
- Google has Chrome which uses Blink (forked from Webkit)
- Microsoft has Edge which uses Blink
- Opera has Opera which uses Blink
... The only two major players currently maintaining a non-Chromium and Blink based browser are Firefox (mentioned by the OP) and Apple (mentioned by myself).
I was simply trying to provide some additional context about the history of Chrome, perhaps I should've also included the context about the history of Safari.
But anyways... blah blah blah
If just rendering engine (but not a browser) then Sciter will qualify I think too. And it is not derived from any others.
if you wanted to publish a document, just ship some bytecode to render a document
want an interactive application? just use a bytecode library that renders controls and textfields etc
browsers then would become much simpler, and pages would just render themselves, meaning super old sites needing "quirksmode" would even be a problem....
i wonder why this never happened... what am i missing...
I don't think the creators of the web ever imagined how it would take off and the kind of scope-creep that would happen even in their wildest dreams. And now we're stuck with the existing formats because doing anything else will likely break billions of old websites out there.