Prior to downloading the Silver Server software, ensure your server allows the download of applications from anywhere.
Select System Preferences > Security and Privacy.
At the General tab, click the lock in the lower left portion of the screen to allow you to edit the permissions. A prompt appears requiring you to enter the administrator name and password.
Type the administrator user name and password.
Click Unlock.
Under ‘Allow apps downloaded from,’ select Anywhere. A prompt appears.
Click Allow From Anywhere.
Click the lock to prevent further changes.
Close Security and Privacy.
Warning:After you download the Silver Server software, return to Security and Privacy and change the ‘Allow applications downloaded from’ setting to Mac App Store for best security.