As promised a few days ago, the RTM build of Windows 8.1 Enterprise is now available to download via TechNet and MSDN subscribers for Volume License customers with an active Software Assurance agreement. The Enterprise SKU of Windows 8.1 has a number of different features compared to the Core and Pro versions, especially in terms of security.
In a post on the Windows for your Business blog, Microsoft links to a chart that compares the features of Windows 8.1 RT, Windows 8.1 Core, Windows 8.1 Pro and Windows 8.1 Enterprise, the latter of which has exclusive additions such as AppLocker, Start screen control, BranchCache and more.
To make sure that our Volume License customers running Windows 8 can experience the great benefits Windows 8.1 has to offer, organizations that acquired Windows 8 Pro through a VL agreement are licensed for Windows 8.1 Pro even if their SA expired prior to the GA release of Windows 8.1 Pro. This does not apply to Windows 8 Enterprise; you must have active SA for the Windows desktop operating system to have rights to Windows 8.1 Enterprise licenses.
Windows 8.1 in both Pro and Enterprise versions will be available for production use via the Volume Licensing Service Center on October 18th and new Volume License customers can buy it from Microsoft Volume License Resellers starting November 1st.
Source: Microsoft | Image via Microsoft