The creator discontinued this mod, but it was updated to 1.1 in this thread. I downloaded it and installed it, it seemed to launch, but firing arrows doesn't work properly and the arrows break very often.
If you guys are interested in seeing it continued, you should go over to that thread and post there. I think he updates things according to popular demand.
Hopefully there is a working zipline mod for the 1.2 official patch, which is where it could gain mega-popularity.