I am the principal of a small consulting practice, reviewing large amounts of documents in order to prepare reports for my clients (who are mostly attorneys).
DT3 runs on my main home office Mac. No special computer needed - it runs on the same iMac I use for my regular work.
There are several uses for the web server in this situation:
(1) If I am out of town or otherwise away from my regular computers with DT3 installed, I can still access any needed document and either view it on the web or download it to whatever computer I am using
(2) My staff can upload new documents to the web server as well as notes or metadata/tags/labels to help me track due dates or other important tasks related to a given case. The staff do not need DT3 installed on their computers in order to do this.
(3) I have not done this yet, but I could set up client-specific databases so that clients can upload documents or review my completed report on the case or enter comments about the project. My clients do not need DT3 installed in order to do this.