You need to download the "osm generic macosx.zip" and this will extract to the file "OSM generic routable(THA_19-01-2015).gmap" and that when double-clicked will install on the mac using Garmin MapManager.app I think and Basecamp on the Mac will load it fine. It worked for me ok. You may have downloaded the Windows or Linux file by mistake or got amongst the "Nullsoft Scriptable Installer script used to create the BaseCamp/MapSource installer." which is probably a Windows thing? ![file list][1] [1]: http://help.openstreetmap.org/upfiles/Screen_Shot_2015-01-23_at_12.15.53_am.png/upfiles/Screen_Shot_2015-01-23_at_12.15.53_am.png

You need to download the "osm generic macosx.zip" and this will extract to the file "OSM generic routable(THA_19-01-2015).gmap" and that when double-clicked will install on the mac using Garmin MapManager.app I think and Basecamp on the Mac will load it fine. It worked for me ok. ok. You may have downloaded the Windows or Linux file by mistake. mistake or got amongst the "Nullsoft Scriptable Installer script used to create the BaseCamp/MapSource installer." which is probably a Windows thing? ![file list][1] [1]: http://help.openstreetmap.org/upfiles/Screen_Shot_2015-01-23_at_12.15.53_am.png

You need to download the "osm generic macosx.zip" and this will extract to the file "OSM generic routable(THA_19-01-2015).gmap" and that when double-clicked will install on the mac using Garmin MapManager.app I think and Basecamp on the Mac will load it fine. It worked for me ok. You may have downloaded the Windows or Linux file by mistake. ![file list][1] [1]: http://help.openstreetmap.org/upfiles/Screen_Shot_2015-01-23_at_12.15.53_am.png