A few weeks ago, on the same evening I wanted to start improving keystone somebody appeared on kde-devel and said that he implemented a QT-based VNC client and wants to port it to KDE. So I gave up the keystone idea, even though I haven't seen the new client yet and I am not sure whether it will actually see the light of day.
Progress on krfb 0.7 is ok, the KControl module is working, the kded module (kinetd) looks good (but wasnt actually tested). Now all that I need is the invitation feature and make sure that everything works. I hope to get 0.7 out this month. After 0.7 a loose code freeze will start, and I only plan to do bugfixes, maybe add some minor features and, of course, documentation and i18n stuff.