A while ago we announced that we were making the VHD format available, royalty free, to people who were interested in using it in their products. Today we have announced that we are releasing this format under the Open Specification Promise (OSP). If you are not familiar with the OSP – checkout: http://www.microsoft.com/interop/osp/default.mspx. In layman’s terms it means – go for it. Use it for free – it is fine by us.
For more details about the VHD specification – checkout: http://www.microsoft.com/windowsserversystem/virtualserver/techinfo/vhdspec.mspx