Azure will be available through the Open and Open Value programs from 1 August 2014. Customers will buy $100 Monetary Commitment SKUs from their resellers which will be fulfilled via an Online Service Activation (OSA) Key. These keys last for 12 months from redemption and there will be no refunds for unused credit or the opportunity for it to be rolled-over to the next year.
Read the Microsoft announcement here http://bit.ly/1krpLnP and find a link to a presentation, datasheet and FAQ.