One was released after no longer being considered an "enemy combatant" and the others after it was determined they could be transferred, officials said.
and the Pentagon says other releases are being considered, in this highly informative (not) official-speak:
"Departure of these remaining detainees approved for transfer or release is subject to ongoing discussions between the United States and other nations."
I think it is pretty clear that this US Administration is squirming and trying to contrive plausible reasons for shutting down this legal monstrosity whilst at the same time pretending it has been justified in holding people there in extra-judicial limbo, without charge or trial, for excessively lengthy periods. Bush's speech earlier this week during his visit to Austria made for very interesting listening - he is on the hook and he knows it, even if he still must placate his support-base (such as remains) back home.