AppJet's free hosting (AppJet 1.0) being discontinued
appjet.com
appjet.com
Everyone running on Google App and all the other Rails services will have the same thing happen to them at some point. Stick with stuff you can migrate.
It's like this: A guy tells you he will ferry you to England for free. Half way there, he says - hmm, actually, I've changed my mind. I'll take the engine, but here are two paddles - see ya!
Of course it's quite different from appjet, but I'd say it's the same category: hosted, rapid web tool development.
And it costs me almost nothing to run, so there's no reason I'd ever take it down.
For the text syncing part there is an excellent free library from Google: http://code.google.com/p/google-diff-match-patch/
But onward and upward, and best of luck to the AppJets (or now, the Etherpads). They're super bright guys, so it's not surprising at all to see them succeeding.
Good luck, guys!
I think I may make a page someday with all the things I said would happen to the companies and what actually did happen.