Wikimapia (Wikimapia.org) is a collaborative community mapping project, which has a few things in common with OpenStreetMap, and can be said to compete with OpenStreetMap (at least in terms of attracting attention and contribution efforts). So how do the projects compare?
License (and imagery derived data issue)
Wikimapia contributors trace Google imagery. Because their data is largely based upon (geo-located using) aerial imagery provided from Google Maps, the dataset may constitute a "derived work". This is dependent on jurisdiction, and generally an unclear area of copyright law, but it's a well established legal principle which allows aerial photography companies to license their exclusive right to derive geo-data from their imagery (commercially, or under proprietary restrictions). Although Google are not known to have launched copyright actions in the courts over use of aerial imagery, their terms of service do include a specific provision barring 'derivations' without a license from Google.
Open licensing is fundamental to the stated mission of OpenStreetMap, and our community have always taken care to source geo-data from their own surveying work or from sources which do not compromise our open licensing. In this way we build on secure legal foundations to power an exciting ecosystem of data use and re-use. When it comes to tracing imagery, we carefully avoid tracing geo-data from Google maps, and instead we use Bing and other sources for which we have agreement (agreement to derive vector data and release it with our open license), or sources which are copyright free. Over 20 imagery layers are available to us. This does not include Google imagery.
We should stop short of saying that Wikimapia are wrong to state CC-BY-SA. There is a certain category of trivial/tangential geodata uses, where data users would be unlikely to concern themselves with this derived data issue. But the derived data issue does mean that Wikimapia are not really building an open data ecosystem in the same way.
This also means we would never import data from Wikimapia, since it doesn't meet the kind of clean-room licensing standards which we expect of OpenStreetMap input data.
Wikimapia data model is very restricted, therefore, along with license considerations, not suitable for serious GIS uses. OSM data is suitable for serious uses, due to clean-room criteria and rich data model encompassing almost all geographical aspects.
Putting OSM data into Wikimapia is not allowed
OpenStreetMap data is licensed under ODbL. It's a license very similar to CC-BY-SA, but not the same. It's also unclear whether Wikimapia are disallowing commercial use (that would obviously be a very big license difference) In any case transferring data from OpenStreetMap into Wikimapia is not allowed. This would be re-licensing our data without permission. An infringement of OpenStreetMap copyrights.
This does include transferring data from OpenStreetMap by tracing over rendered OpenStreetMap maps. The act of tracing raster data back into vector data is still copying. In fact Wikimapia at one stage offered up OpenStreetMap standard map tiles to their users as an optional base-map for tracing in data. Because this was encouraging a breach of copyright, Wikimapia was in violation of the Tile usage policy, and their use of our tile server was blocked.
This does not include data which you have added to OSM yourself. If you surveyed an area and input your own data in OpenStreetMap, you can input that data into Wikimapia, and whatever other systems you wish. This means you might choose to contribute to both OpenStreetMap and Wikimapia as in both cases user agree to grant non-exclusive license. In this case, it is recommended to contribute to OSM first and then to Wikimapia.
Their moderation system and power user system
The Wikimapia system automatically assigns "experience points" to editors for various editing actions, and ranks them in levels according to points earned. Higher levels have increased access to editing tools and fewer restrictions on editing activity.
Editors at the top levels be invited to become "moderators" or "power users". As such they receive additional editing rights, access to more map-monitoring facilities, and authority to ban users. Those power users do most of the work of managing other editors, including establishing rules and fighting vandalism.
By contrast everyone in OpenStreetMap can edit anything at any time.
Wikimapia has a simple online editor for adding geo data. We could probably learn some lessons about simplicity from this!
With OpenStreetMap you can use the most sophisticated tools from day one. We provide you all possibilities for productive mapping.
ID is a simple online editor at https://www.openstreetmap.org/ Many mappers use the JOSM editor among many other tools. These typically let you edit 100 or 1000 elements per day. In fact it is not rare for OpenStreetMap contributors to talk about 10k-30k elements changed per day. This is almost impossible to happen within Wikimapia community.
Tools include (list is not full):