I guess people have forgotten, that Webkit came out of KHTML from the KDE team and that Apple was a nightmare when it came to contributing code back. They just released a huge dump of the whole thing.
When you have a long-running fork, especially one that is so active, merging it naturally becomes a nightmare. This is expected and ordinary.
The Linux kernel gets forked by Android vendors and others all the time. A lot of the changes never make it upstream, for various reasons. At least the story ends a bit better for KHTML / WebKit.