WebKit isn’t proprietary. Ultralight, the thing I linked to, is a fork of it.
You’d just need to build a UI.
webkit != safari. You might "just" need to build a UI, but if you want it to be cross-platform, that brings you back to the question of what GUI toolkit to use, or you have to handle the mess of different APIs for different platforms yourself.
You’re really confused. We’re not talking about a browser, just an app platform. You can build WebKit on every major platform. If you’re talking about including a UI kit, there’s unlimited of those already written in HTML/CSS/JS. Once WebKit is running there’s no “different APIs”... that’s the whole point.
I'm really curious how you would fork a proprietary project.
> If someone did that, I think we'd have a really ideal setup for cross platform apps.
Buy safari isn't cross-platform.