The latest installer beta has the wrong link in the RemotePackages.plist file for the BSD subsystem.
RemotePackages.plist is in /var/root/library/installer/
You need to change
<string>http://conceitedsoftware.com/iphone/zips/BSD_Subsystem-1.5.zip</string>
TO
<string>http://iphone.nullriver.com/zips/BSD_Subsystem-1.5.zip</string>
Then open installer.app and immediately install the bsdsubsystem, I say immediatly, as you dont want installer.app to do one of its sources refreshes, and undo the work you have just done!
RemotePackages.plist is in /var/root/library/installer/
You need to change
<string>http://conceitedsoftware.com/iphone/zips/BSD_Subsystem-1.5.zip</string>
TO
<string>http://iphone.nullriver.com/zips/BSD_Subsystem-1.5.zip</string>
Then open installer.app and immediately install the bsdsubsystem, I say immediatly, as you dont want installer.app to do one of its sources refreshes, and undo the work you have just done!