Officially As a Part of the Microsoft HoloLens Community

I just received the email from the Microsoft HoloLens Team that my application for the Microsoft HoloLens Development Edition has been approved!  After the Build 2016 Event on March 30 - April 1, Microsoft announced the availability of the HoloLens Development version for qualified application developers.

To develop software for HoloLens, your develop PC must have Windows 10 Professional version with GPU capable of  DirectX 11.0 or later.  Only professional version support Hyper-V.  For the software portion, you need to install the VS 2015 Update 2 and community version is sufficient.  Unity HoloLens Tech Preview Beta 10  http://unity3d.com/unity/beta  Unity 5.4.0B13 (4/4/2016)

If you encounter an error when you tried to install Unity, such as "'WSA' does not exist in UnityEngine.VR", this means that you need to install the Unity Editor first!  http://unity3d.com/pages/windows/hololens

Run as Adminstrator on this UnitySetup64(1) - 311 MB
C:\Program Files\Unity Hololens 5.4.0b10-HTP\
Then you can install the UWP runtime: Install UnitySetup-Metro-Support-for-Editor-5.4.0b10-HTP 

Finally, there is HoloLens Emulator.  Although the requirement for installation is Windows 7 SP 1, it is useless since VS 2015 is unable to run the HoloLens emulator if your OS is not Windows 10.  

The emulator allows you to run apps on Windows Holographic in a virtual machine without a HoloLens. This package also includes holographic DirectX project templates for Visual Studio. Here is a screenshot of the emulator installation.  It may take a while!

Building HoloLens apps will be an exciting experience since we can make something in the virtual world and bring them to live by mixing them in the reality and be part of your real world.  It's an amazing journey!