AWS GovCloud (US) Region is an isolated Amazon Web Services environment used by US government agencies at the federal, state, and local levels, along with contractors, researchers, educational institutions, and other US customers.
In terms of boxes checked, GovCloud has received the following certifications:
For more information on AWS's compliance with federal and other standards, see AWS's compliance page.
For installation purposes, GovCloud is treated like any other AWS region. Simply follow the steps for Installing GitHub Enterprise on AWS, being sure to select the 'us-gov-west-1' specific AMI ID.