In more recent versions of Android (my Galaxy S4, for example) the call to getExternalStorageDirectory() no longer gets the external storage. It returns /storage/emulated/0/, and on the S4 this is internal storage (which is limited in size). The external card is at /storage/extSdCard. For a data-intensive app such as OruxMaps, this can eat up the internal storage.
I found I could individually change the settings to use /storage/extSdCard/oruxmaps for maps. tracks, and waypoints (the directories customwpts, geocaches, mapfiles, mapstyles, overlay, pictures, and tracklogs). I moved the ones originally in /storage/emulated/0/oruxmaps to /storage/extSdCard/oruxmaps.
However, on restarting OruxMaps, it recreated the ones in /storage/emulated/0/. I am not sure what it is using. (The settings still have the /storage/extSdCard ones.
This may not be a bug, but it is is a problem that should be addressed (to avoid filling up internal storage, if for no other reason).
If there is a way to do this that I missed, I apologize. I didn't see it.