It’s official. Forty minutes ago Microsoft put out a post Introducing Microsoft Dynamics GP 2013 R2. It’s available for download now on Partnersource.
Introducing Microsoft Dynamics GP 2013 R2 – Microsoft Dynamics ERP “The Edge” Blog
Microsoft & the GP EcosystemGP 2013
Archived post from 2014. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.