In Fabiano source, you can just use the .jm as a map instead of converting it into a .wmap file. When you upload it to your worlds folder you will follow the same steps as using a .wmap file such as changing its properties to Embedded Resource, but when you are in the World Class file for your world. you will need to change MapType.Wmap to MapType.Json and the extension of your map's name to .jm .
Example:
LoadMap("wServer.realm.worlds.maps.spiderden.jm", MapType.Json);
Please remember that some World Class files may already contain these changes.