I am glad to announce that with the release of RadControls for Silverlight Q3 2009 Service Pack 1 RadMap has been updated to support OpenStreetMap provider. It is as easy as setting a single property:
MyRadMap.Provider = new OpenStreetMapProvider();
Set the Center and Location properties and you are ready to go. Here is an example of RadMap with our Boston office address in the center:
<map:RadMap x:Name="RadMap1" ZoomLevel="13">
<map:RadMap.Provider>
<mapNamespace:OpenStreetMapProvider />
</map:RadMap.Provider>
<map:RadMap.Center>
<mapNamespace:Location Latitude="42.397223" Longitude="-71.254685" />
</map:RadMap.Center>
</map:RadMap>
And this is the result
You can find a link to a sample project in the beginning of this blog post.