There isn't a load of benefit to having a read only OSM API database. If you want to load the data into an OSM editor like JOSM, you can open an OSM XML file. I

There isn't a load of benefit to having a read only OSM API database. If you want to load the data into an OSM editor like JOSM, you can open an OSM XML file. If you want to render maps from OSM data, you have to load it into postgresql with osm2pgsql which works with OSM pbf or xml files. A local API db is rarely useful.