Wohoo, I’m super excited because the next release of Gridmapper will do away with auto-saving and auto-loading. Instead, it will use a small server component on Campaign Wiki and allow users to host Gridmapper sessions. Thus a mapper could load the page, name his session “Nuclear Doom” and anybody else who knows this name can also load the page and join this session. And it will be more or less in real time because of WebSocket.
Update: Currently it’s not working because of web server issues. Site uses HTTPS and so the requests for the WebSocket server need to get proxied from Apache to the backend using
mod_proxy_wstunnel.  This module requires Apache 2.4 and I have 2.2.22 installed – I’m still running Debian Wheezy. Trying to compile and install just the module failed.  So right now, I’m stuck. Loading Gridmapper via HTTPS will not allow me to make a connection to the backend using an unencrypted connection, and that requires the module, which my web server doesn’t support... Gah!
Update: Apparently I need to install both
mod_proxy_wstunnel after recompiling a patched Apache. 
Update: OK, it seems to be working, now. And with less weird error messages by Chrome. I had to use Hypnotoad instead of Toadfarm because there can only be a single worker. After all, all the maps, clients and servers are stored in memory and not on disk. The names of the maps currently being hosted can be seen from the web page that goes along with the server component:
Update: When you’re hosting a map, the page above will now offer a link to join that map. Thus, here’s how you start your session: