One use-case is to have a VNC client in Google Chrome OS / Chromium OS http://www.chromium.org/chromium-os

The point of the Guacamole, Carde, jsVNC and the like is to have VNC-client in the browser without any other requirements. Other approaches require a java runtime environment (TightVNC, UltraVNC etc. the stuff that people say they have been doing since 1998), flash-plugins (FlashLight-VNC) or as the case with Gitso you have to install an native client.

The only client-side requirements for Guacamole and jsVNC is to have a browser with HTML5 canvas support! Nothing else!

In the comments people seem annoyed by the java backend, the VNC-to-XML parsing and the project name :)

A different project with a spot-on name: jsVNC (http://code.google.com/p/jsvnc/) is out there!

  * What a nice name :)
  * Uses websockets, no XML encapsulation. Falls back to XHR, if websockets are not supported. The XHR-fallback neither do any XML-encapsulation or JSON encapsulation (done by the Carde vnc client). This is done to obtain minimal payload encapsulation.
  * Uses a python backend (not java) for websocket/xhr -> socket translation, this backend can also do some other neat tricks, see: http://code.google.com/p/mifcho/

The jsVNC project however does not have any releases yet. But I expect to have the first release around august. Yeah i said I... this is a shameless advertisement for my quite on-topic and quite related project :)