Pam offers some GP 2013 licencing clarification with Perpetual Pricing Top Tips
Perpetual Pricing Top Tips – Inside Microsoft Dynamics GP – Site Home – MSDN Blogs
Tips & Hidden FeaturesMicrosoft & the GP EcosystemGP 2013
Archived post from 2012. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.