Reading blogs this morning, I ran across Brad Neuberg's announcement that he is working for SitePen to create an off-line Dojo toolkit. I have to get ready for my day job now, but I'm excited enough that had to write something first. This is really step #1 to creating a WebOS.
I've mentioned in the past how a client-side server is required to create a proper WebOS. That seems to be exactly the approach Brad is taking.
I also commented to Brad that Scrybe seems to do the off-line work without a proxy, though they may just be leaving that out of the demo information.
The great news, however, is that Dojo is a really popular open source toolkit and should get a lot of traction, even if it isn't on as many platforms as possible from the start. Brad also seems to be a really smart guy.