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