This path was initially used for compatibility with Maemo MApper/Mappero - the modRana POI database format is based on & compatible with the Mapper/Mappero one. POI database sharing is off by default but can be enabled in Options->POI->POI storage. Sure, it definitely makes sense to add a configuration file option to redirecting the POI database storage path, so noted.
Yeah, unless someone steps up to maintain it or to develop it further, it is pretty much depreciated at this point. Still, I think I'll try to at least keep it working in its current state on a reasonable effort basis. Also I'm thinking about splitting it to a subpackage as it currently drags in quite a big amount of dependencies even for people using only the GTK GUI.