"It's a LAN-party like feeling for map enthusiasts, and because you may have blood-shot eyes after 8hrs of non stop mapping, we decided to give it a zombie theme," the wiki announcement says. The mapathon is open to experienced "OSMers" and novices alike.
To participate, join a party near you or start your own. And it might not even be necessary to BYOB! "The OSM Foundation and the FOSSGIS e.V. will support your local party with a small amount of money, so you can buy junkfood and drinks," the announcement says.
After the event, check out the Results page to find out what other mappers did during their sleepless night. Are you planning to participate or organize an event in your area? If so, let us know about it in the comments. Happy Moonlit Mapping!