Antivirus protection for dedicated music server like SGC Sonictransporter?

Maybe with the correct router with router antivirus. 

You would need to contact Small Green computer. Anti virus software is specific to the operating system your device is running. They would tell you what anti virus software will work (if any) and how to initiate scans (if possible). More than likely you will not need to run any anti virus software. Keep a backup of your music in an offline storage device just in case by some small chance the server gets infected. In that case reinitialize the your system.

Thanks to both of you. I sent an email to Andrew, but in the meantime I’ve resolved the concern in my own mind, and went ahead and ordered the Sonictransporter.

the issue is closed . . .

The sonicTransporter is an embedded music appliance like a router or NAS. I can not get a computer virus so this is not something you need to worry about.