I’ve just had my attention drawn (by the good folks at EDINA) to the Peer-to-peer GIS project and the OPen Use Server (OPUS). The link refers to their implementation being based on Java, Apache, PHP and MapServer. It also says that it is based on RoMap.net (Rapid Online Mapping Network), and they say that

RoMap is a set of peer-to-peer protocols and network infrastructure to allow compliant GIS applications to work together over a network.

I can’t yet find any real information on ROMAP beyond what fgdc says about the project. Annoyingly there would appear to ought to be a link to a website http://romap.net, but at the moment that goes nowhere …

Anyway, the FGDC says that they funded it with OGC, and given it’s based on Mapserver, I’m guessing that OGC Web Mapping Server protocols underly how it works.

When I get a moment (ha, famous last words), I’ll contact the authors and find out a little more about it …