Latest part of the story. News.com has an article about how Apple want KHTML developers to use Apple WebCore tree...
Here is the KHTML developers point of view. They seems to still be motivated, or at least to not have lost any hope about that.
The main problem I see is that using Apple CVS tree requires to have an ADC account and to to have an ADC account, you have to be over 18 as per Apple agreement:
By checking this box I confirm that I have read and agree to be bound by the Apple Developer Connection Terms and Conditions. I also confirm that I am 18 years or older.
That would have been fixed prior to any committment. Apple's definition of open source seems to require to be 18. Note that this is not to obtain the software as a tarball, but to obtain a CVS account... At least that is my understanding.