Greetings!!!
Advanced Open File Option(AOFO) is per server basis. Therefore, if you wish to protect 4 servers using AOFO then you would require 4 licenses. You may contact the sales department to purchase the licenses.
Please get in touch with our local sales representative. Alternatively, you can contact our local sales office. You can locate them using following link:
http://www.veritas.com/contactus/ContactUsHome.jhtml
As far as installing these options in eval mode is concerned, they cannot be installed in eval mode separately if Backup Exec is licensed. You may however, install Backup Exec in evaluation mode on a separate test server and evaluate the options.
You may refer the following links:
http://support.veritas.com/docs/253168
We hope this helps.