Duplicity is just the backend for TKLBAM so you could use it on it's own (without the TKLBAM frontend). AFAIK it's in the standard repos so should install fine with apt-get.

As for hacking TKLBAM, I haven't even tried (the point of using it for me is for remote backup - I do local data backups myself separately). There have been suggestions/requests in the past to be able to host local instances of the Hub and it's something that I think would be cool. AFAIK the devs have considered it but haven't yet decided whether it's something they'll do. Even if they do, I don't think they'll be working on that anytime soon. They have a todo list a mile long and with Ubuntu 12.04 (the basis for the upcoming TKL v12.x release) just around the corner I don't think it's going to slack off for them anytime soon!

As TKLBAM is open source, there's no reason why you couldn't have a play with it and see what you can do. Although without being attached to the Hub, it's perhaps just as easy to use Duplicity standalone