RTW version of Active Directory Management Gateway Service (ADMGS), an Active Directory Web Services (ADWS overview here) out of band release for down level servers is now available to download from Microsoft Download Center Page. ADMGS is a down level release of in-box version of Windows Server 2008 R2 ADWS and provides the same functionality. One can download and install ADMGS on servers and domain controllers running the following operating systems:
ADMGS enables administrators to use Windows Server 2008 R2 or Windows 7 client applications such as the Active Directory module for Windows PowerShell and the Active Directory Administrative Center (ADAC) to access or manage their existing Active Directory Domain Services (ADDS) and Active Directory Lightweight Directory Services (AD LDS) instances that are running on Windows Server 2008-based (both writable and read-only) or Windows Server 2003-based servers.
The only difference between the functionality that ADWS provides for domain controllers that are running Windows Server 2008 R2 operating system and the functionality that ADMGS provides to domain controllers that are running Windows Server 2008 and Windows Server 2008 SP2 operating systems is that ADMGS does not support instances of the Active Directory Database Mounting Tool running on Windows Server 2008-based servers.
Downloadable install guide at the same location provides information on ADMGS installation, uninstallation and upgrade scenarios.
Developer - Active Directory Web Services team