Software Assurance now includes the full features and capabilities of MDOP. MDOP is a set of products to help with virtualization, management and restore capabilities. With the Windows 10 launch, MDOP is now included as an SA benefit, and is no longer a separate add-on.
If you have installed the Windows 10 Preview like a lot of people but experiencing lockups, bugs, etc, before reverting back to Windows 8.1, try a full reset first. Many times the in-place upgrade to Windows 10 Preview can cause issues just like doing an in-place upgrade on the desktop. Having a clean start often clears a lot of problems.