Back when Safari first came out, there was a lot of credit given to KHTML, and Apple quickly had public-facing Subversion repositories available with full product history so that KHTML could adopt any changes they wanted. Since then, WebKit and KHTML have gone radically different directions, to the point that I'm not honestly sure the latter exists anymore.
Apple, I thought, did the right thing by providing a full hat-tip to KHTML at the time of the fork. I also think their attitude towards KHTML since then has been completely fair.
For quite a while, Apple were jerks about contributing there changes back. The patches they submitted to KHTML were huge, undocumented, and full of OSX-specific code. It tooks many months of griping by KHTML, GPL advocates and the community before Apple opened up thier KHTML fork as a CVS repo, and some time later, simply open-sourcing Webkit itself. But at the beginning, it was quite a fight to get Apple to acknowledge Webkit's open-source roots.
The KDE project has now dropped KHTML and switched to Webkit.
This is inaccurate, KDE still uses KHTML. I've certainly seen the point argued back and forth amongst KDE developers, but all versions of KDE still use KHTML, and I assume it's still maintained somewhat. KHTML and WebKit aren't just interchangeable pieces of Konqueror, see http://www.kdedevelopers.org/node/3998 .
thiago from #kde informs me that "the guy [who claimed that KHTML is gone] is completely wrong", "[KHTML] is happily in use and cannot even be dropped yet".
I was also informed that "there are plans [to change to Webkit], but they're slowgoing" and "nothing concrete has happened yet". If anyone has access to an official announcement to this effect, I'd appreciate a link, because last I knew there were just developers bickering back and forth about which to keep.
Also, I assume that with WebKit SFX would become the KDE browser's JavaScript engine instead of KJS, and that would be nice. KJS is much slower in my experience.
Apple, I thought, did the right thing by providing a full hat-tip to KHTML at the time of the fork. I also think their attitude towards KHTML since then has been completely fair.