Thanks. I didn't really get much of a chance to use it in a live environment, so I don't know the kinds of features that were desired. I looked into it for another reason, and eventually found that SpecLog's sister project, SpecFlow, was a better fit for the needs.
I'll answer your questions as best I can.
SpecLog is a Windows/.NET 4.0 application. As far as I'm aware it only runs via Windows, but it has several export options for HTML, PDF, or spreadsheets. It also connects to a Microsoft SQL Server on the backend (this is optional, but likely ideal for the OP's scenario). Theoretically, one could create an interface for non-Windows users simply by calling a few queries and building a front-end for it.
The software allows for multiple projects, each would appear as a "page" or tab. Within the project is one massive editing area, which can be made larger than the viewable area. I didn't try editing with multiple clients, so I'm unsure if the project can be edited simultaneously by multiple people remotely, but considering it's simply built on a SQL server, it could probably be edited in near-real time, just not real time. SpecLog's doc wiki claims multiple clients can edit in parallel.
There's no moderator, access is pretty all or nothing. Either someone has access to to edit or they don't.
An external solution would need to be found for video/audio conferencing.
Hope that helps!