We are currently investigating reimplementing the 'Tinsel' engine, as used by Discworld 1 and 2.
Ender is organising this.
The rights situation has been resolved, and Terry Pratchett and his agent Colin Smythe have approved the source release and future freeware re-issuing of the game.
We are currently awaiting news on the engine source code.
The last update (23rd March 2005) suggests there will be more definite action by Mid April.