Apple discontinued Server Admin.app starting with 10.8. Which is unfortunate because Server.app doesn't have the functionality of its predecessor when managing multiple servers with differing OS versions.
I found a work around to get Server Admin.app "working" on 10.8:
From a 10.7.4 server Mac, copy the following two items to your 10.8 Server:
/System/Library/PrivateFrameworks/GeoKit.framework/ServerKit.framework
/System/Library/PrivateFrameworks/GeoKit.framework/Version/A/GeoKit
The GeoKit binary already exists on 10.8, so be sure to back up or rename the original in case you ever need to go back.
Next Install Server Admin Tools 10.7 using a shareware app called Pacifist. This allows you to get around the Installer PKG's OS limitation.
finally open Server Admin.app via terminal:
open "/Applications/Server/Server Admin.app/Contents/MacOS/Server Admin"
Vola, Server Admin.app opens. Don't try managing 10.8 systems with it as the causes the program to crash out.
Hopefully Apple will add the missing features to Server.app so hacky workaround like this won't be necessary.
