Please note it is a custom version of DriveHQ FTP server, not based on UNIX, not based on Windows.
You always have full access right to your own files. So you cannot  make a file to read-only when you log on yourself. But when you share  the file / folder to other users, you can set the share permission to  read-only. You can do so using DriveHQ FileManager 4.0, or using our  website, logon and go to Online Storage & Sharing.
When other users logon DriveHQ, they can access folders you shared to  them in the special virtual folder: \DriveHQ Share\YOUR_USERNAME
We have our own proprietary FTP server.  Please download File Manager  and go to Tools -> Manage Shares.  You can change the permission this  way.  Download FIle Manager here: http://www.drivehq.com/downloads/downloads.aspx