I can't comment on the state of things today, but I was active an active KDE core developer at the time from that original message to the time of the Zack's blog post (and I'm friends with both Dirk and Zack):
There was a huge amount of excitement at the announcement that Safari would be using KHTML. At that time, it was almost a given that the OSS rendering engine was Gecko. KHTML was KDE's little engine that could. But nobody ever expected it to be picked up by other folks. One of the original parts of the KHTML-to-OS X port was KWQ (pronounced, "quack") that abstracted out the KDE API portions that were used in KHTML.
Folks were pretty ecstatic at first. It seemed very validating.
But that changed quickly. As Zack's post indicates, WebKit became a thing of unmergable code-drops. Even inside of the KDE community there became a split between the KHTML purists and the WebKit faction. They'd previously more or less all been KHTML developers, but post-WebKit there was something of a pragmatists vs. idealists split. Zack fell on the latter side of that (for understandable reasons: there was an existing community project, with its own set of values, and that was hijacked to a large extent by WebKit).
A few years later WebKit transformed itself into a more or less valid open source project (see webkit.org), but that didn't close the rift in the KDE community between the two, at that point rather divergent, rendering engines. There's still some remaining melancholy that stems from that initial hope and what could have potentially been, but wasn't.
It's hard to argue that WebKit being open source has been a bad thing -- in fact, I don't believe that in the slightest. But I can also understand that it's pretty head-turning to have have a project transform in that way, especially for the original contributors (though, it should be noted, the original author of KHTML, who wasn't really active at the time of the transition, did eventually fall into the WebKit camp).
Final note: this is just my somewhat fractured recollection of things from being in KDE community. My contributions to KHTML / WebKit were very minor (the original spellchecking support) so this may not jive completely with the folks that were closer.