Hi kwg, sorry for the delay - I didn't find your post somehow...
Your assumption was correct. WebShield is meant as a desktop (workstation) provider and as such is included in avast Server Edition only for the Terminal Servers case.
The "Server Deployment Wizard" that gets automatically started after you install avast should disable it automatically (together with other desktop providers such as Internet Mail, Outlook/Exchange etc.)
Thanks
Vlk