This was the answer to your earlier post, see below for an answer to your latest...:
that's great :-) I would advise against Xfbdev in such a scenario, since both Xfbdev and kindlevncviewer would use the framebuffer in such a case and this might cause conflicts or artefacts, I think.
Using VNC, even with "copyrect", still means that data is shoveled through the kernel's networking layer and replicated onto the framebuffer. I think it would be interesting to patch x11vnc to _not_ encode recognized changes and send them via VNC, but plug kindlevncviewer's screen update method into the code at that point. Will see if I can come up with something like this...
Well, best thing to have would actually be a working Xfbdev. I didn't dig too much into the XOrg code yet, but maybe that would make even more sense. There should be some way to overcome that nibble-in-byte order problem...
The documentation for x11vnc is in fact, erm, extensive: http://www.karlrunge.com/x11vnc/
(plus the FAQ!)
See the various mentions of Xvfb, Xdummy (need to check that one, I think buildroot can build it too with the modular Xorg!) and x11vnc's -create and -display switches. In fact, the amount of documentation makes my head hurt :-)