Jeff:
There is no single tarball with the entire Hortonworks Data Platform (HDP) software. Instead, our software consists of a number of packages prepared for OS-specific package managers. These packages can be installed automatically via Ambari, or manually, and the resulting cluster will be customized to your requirements. We do maintain repositories, which can be referenced for the HDP software.
I recommend a review of the manual or automated installation guides, which can be found at the Hortonworks documentation site, http://docs.hortonworks.com/. These provide guidelines on how to set up systems for installing HDP software, as well as how to install and customize an installation.
Happy hadooping!
Bryce Ryan