Wording added to the July 2013 PUR (page 88) about using Remote Desktop Services with Windows Azure Virtual Machines (although expect more changes next year):

• RDS Subscriber Access Licences purchased through SPLA MAY be used to deliver graphical user interface functionality on Windows Azure virtual machines
• RDS CALs purchased through Volume Licensing programs may NOT be used with Windows Azure virtual machines
• Virtual Desktop Infrastructure functionality may NOT be used on Windows Azure virtual machines