Its a bit more than a bit of sky software. Those boxes are built to Sky's spec including the NDS Conditional Access hardware.
However you can use it as FTA receiver right now. Unfortunately it will have Sky's EPG which won't contain channels that do not subscribe to it.
The better news is that in order to view Ch4 and Ch5 you have to have the NDS hardware and a Sky Viewing card. An old one with lapsed subscription will do.)
Alternatively you can buy completely non-sky locked boxes for about £40 - but they won't get Ch4 and Ch5.
t, January 2008