Ubuntu Builder, written in Gambas, is the tool which has been used to produce many well working editions of Bento among which the latest Bento 64bits just released.
The announcement, as of March 10th, is clear:
https://launchpad.net/ubuntu-builder/+announcement/12508The author, Francesco Muriana, presented his regrets, and the reasons of his decision. He has worked on it for four years and doesn't have enough time available left to pursue.
I am hoping someone will take on.
