In reply to:
How do I go about installing it on Dreamhost, so that I can call it from a PHP script?
Well, I suppose that you could try to install it via the shell following the instructions in the FAQ on the site, but I wouldn't recommend it.
You might get it to work, with sufficient futzing about with paths and permissions (I cannot tell from the documentation if you can casually manipulate paths/permissions as might be required for you to install it on DreamHost)
DreamHost allows access to the shell and because of that you can install a good many things that you won't be able to successfully run on the DreamHost webservers because of their CPU/memory requirements, their processing time, and the resulting impact on other users serving web pages (the *main* purpose of DreamHost webservers). 
This package looks very much to like it falls in that category.
--rlparker