The emulation is unchanged in the current versions so they will work fine with your SCO server.
The proper way to update your clients is to install the update onto the machine hosting the PRO license server and do a full install.
First, backup your License folder (under TCP5_USER) and copy down your current licenses and company name by running licenseadmin on the PRO license server machine.
Download and install the update on the PRO license server. If you use that machine for a client, do the client install as well.
Run licenseadmin and check to make sure your licenses and users are still there. If they are then skip to the next paragraph. If not, reenter the licenses and company name if they don't show up in licenseadmin and copy the backuped License folder over the top of the one in TCP5_USER. Rerun licenseadmin, you should be able to see the licenses and users.
Now you are all set to install the new version of PRO on your new machine by simply doing the usual network install. (Browse to the TCP5_USER share on the machine serving as the PRO license server and run the setup.exe program).
Ideally, at some point you should update the other client machines. A network install just like on a new machine should update the existing client and leave the settings intact (you should only need to get a sequence number, not a profile).