ethOS is a 64-bit linux OS that mines Ethereum, Zcash, Monero, and other GPU-minable coins.
For login download credentials, search your email for "gpushack". Your username/pass are in the email purchase confirmation.
Per the ethOS license agreement, you must purchase one license per rig for each rig on which you plan to run ethOS. If you need additional licenses, you can purchase them at gpuShack.