It was set up for tourism through a Peace Corps initiative originally by Joe Kennedy (grandson of RFK). Back then it wasn't set up for tourism, but locals would often go there (and they still do, at least half the people there were Dominican). There also were no safety precautions and somebody actually died because of it.
It was a lot of fun going both up and down. It was really good to get some physical exercise, for one thing, but the water was very pleasant and the jumps were exciting. The biggest one is probably 20 feet or more. I really hesitated before jumping off that one!
I kept thinking about a place in Costa Rica just like this. It's inside a park, so it wouldn't be able to be set up like this, but there's really high potential in other places, I'm sure.
I was reluctant to bring my camera along because I was concerned for the housing in all those jumps. But it was fine, and I'm really glad I did. Watch the video of some of the jumps:
I made a stop at Puerto Plata (Silver Port) on the way back to my hotel. My guidebook says you should make it a day trip and stay elsewhere, but from what I saw, it was really nice. Much better than neighboring Sosúa (where I began my trip and where I am staying now). It's not as touristy and people aren't so aggressive trying to sell things.
The fort was built in the 1500s to protect against pirates. The British Empire encouraged piracy in the Caribbean (calling them "privateers" rather than pirates), as a way of disrupting Spanish power in the region. The fort was never used to defend from an attack, though.