Mac OS X is the current operating system for the Apple line of personal computers.
Docbook-X
The easiest method to obtain a working DocBook2HTML or PDF system is to use the promising DocBook-X package created by Julien T. Letessier. You can find DocBook-X at http://www.projectomega.org/subcat.php?lg=en&php=products_docbook.
Other Resources
If you are having trouble with the DocBook-X package, or want an alternate way to get up and running, check out Setting up a DocBook-Environment on MacOS X by Benjamin Boksa. It's a helpful step-by-step instruction for manually setting up the tools.