Caribou is GNOME 3's replacement for gok. It is a themeable on-screen keyboard and library. The standalone caribou tries to intelligently place itself next to the active text input. Unfortunately this doesn't work well in Firefox or in full-screen terminals for instance. It still may improve to be a good competitor to onboard or the basic library could be built into an appropriate Ubuntu-themed screen keyboard similar to what GNOME Shell 3.2 does.
Because Caribou has now been built into GNOME Shell 3.2, we need to get it in the Ubuntu 11.10 repositories or else we risk shipping either an out-of-date GNOME Shell or an ugly patch. Since it is now part of GNOME Core, we can expect it to be maintained.
ricotz has been working with the Debian GNOME team on packaging:
http://anonscm.debian.org/viewvc/pkg-gnome/packages/experimental/caribou/
gnome-control-center has been patched in Ubuntu to load onboard when the screen keyboard has been activated so having caribou in the archives will not interfere with onboard. gnome-control-center could set and look for a gsettings string that sets the preferred on screen keyboard. I don't think we should block caribou based on the g-c-c patch. It should still be possible to run caribou manually (from the command line for instance).
Unfortunately, caribou 0.3.91 doesn't actually run (at least not in standalone mode):
https://bugzilla.gnome.org/show_bug.cgi?id=658533
GNOME Shell doesn't need caribou to work though, just that it's installed.
I'm ok with this as it doesn't break control-center, and blocks gnome-shell updates. Supposedly upstream will work on the startup failure in standalone mode.