The project has attracted over 100,000 users since last March alone, noted founder Steve Coast. He predicts that, given this rate of growth, the contributor base will reach a million by this August.
Coast started OSM in 2004 after becoming distraught over the proprietary nature of world's electronic maps.
"There was lots of open source and free software that you could use with GPS [data], but you couldn't do very much with it because the data was expensive, propriety or badly licensed," he said. "I thought if I could use a GPS [device] to build a map of my area, and others could do it, then we could build a map of the world, with people just mapping their little pieces."
Since then, over 1.3 billion GPS coordinates have been submitted to the project, which have been used to pinpoint the locations of roads, buildings, monuments, hospitals and anything else of interest to contributors.
Advocates liken OSM to a geospatial version of Wikipedia, in which the volunteer-provided content could prove to be much greater in scope than what any single organization could harvest by itself.
Thus far, the basic roads and landmarks of at least a few countries, such as Germany, have been mapped in their entirety, Coast said. In several cases, the project was able to reuse mapping coordinates from other organisations. The US government does not hold the copyright to its geospatial data, so OSM has reused much of its satellite imagery and land attribute maps. British maps that have fallen out of copyright have also been redeployed.
Coast's next goal is to have an entire continent in its entirety. Either Europe or the Americas will be likely to completed first, he predicted.
After the basic information such as roads and notable landmarks is charted, contributors are free to layer on top any other data that can be geographically pinpointed, such as hiking trails or railway lines. "We map whatever is on the ground," he said. "There is no end of what you can map."
The project has inspired the formation of a number of groups that contribute material of some specific region or interest.
One such group is the Washington-based MappingDC, which meets regularly and has a mailing list of about 40 people. Many participants are geospatial experts or enthusiasts of some sort, said Serge Wroclawski, co-founder of the group. It has collected and submitted data on park boundaries, bus stops, even on the locations on the municipality's public trash cans.
To gather more local data, MappingDC established a line of communications with the local D.C. government, from which it subsequently obtained about 300 of the city's geographically oriented datasets. It is now in the process of inserting this data into OSM, Wroclawski said.
On the back-end, OSM is run on about 20 servers. University College London hosts the site, and others contribute bandwidth. About five volunteers maintain the software, and the governance process is overseen by the non-profit OpenStreetMap Foundation.
Unlike Wikipedia, the project has required relatively little funding, Coast boasted. Funding drives have thus far been limited to covering costs to specific items, such as servers or conferences.
The project is still experiencing some growing pains. For the past year, the coordinators discussed moving the licensing that covers contributions from the Creative Commons license to the Open Data Commons' Open Database License (ODL), a move that has generated much debate on the project's mailing lists.
Coast said that while Creative Commons provides only copyright coverage, ODL is far broader, providing coverage for not only copyright law, but database and contract laws as well. Recently, the foundation members voted to adopt ODL, though it will take some more time to switch OSM over to this new license, he added.
Coast said he would like OSM to grow in scope to such a degree that it becomes the world's de facto online map. "We're going to the point where there is no reason for people to use other map data sets because OSM is more easily available, better quality and free," he said.