One month ago today, Microsoft released the RTM versions of Windows 8.1 Enterprise for MSDN and TechNet subscribers to download and use. Today, in conjunction with the Windows 8.1 GA launch, Microsoft has also released ISO builds for both the 32-bit and 64-bit versions of the Windows 8.1 Enterprise SKU.
The download page for the ISO builds state that businesses can install and use these versions of Windows 8.1 Enterprise for free for 90 days. While it's been made mostly for use by IT managers, there's no stopping anyone else from downloading and using these trial versions. However, Microsoft does offer a bit of a warning, saying:
This is evaluation software designed for IT professionals interested in trying Windows 8.1 Enterprise on behalf of their organization. We do not recommend that you install this evaluation if you are not an IT professional or not professionally managing corporate networks.
Windows 8.1 Enterprise has a number of additional features compared to the Core and Pro versions, such as AppLocker, Start screen control, BranchCache and more that make the Enterprise SKU a more secure version of the OS compared to the more consumer oriented versions.