A summary of the reason for their change is here: https://wiki.osmfoundation.org/wiki/Licence/Historic/We_Are_Changing_The_License https://wiki.osmfoundation.or

A summary of the reason for their change is here: https://wiki.osmfoundation.org/wiki/Licence/Historic/We_Are_Changing_The_License https://wiki.osmfoundation.org/wiki/Licence/Historic/We_Are_... Also worth noting is that OSM was on CC-BY-SA version 2 prior to the change. If I'm remembering correctly, version 3 or 4 of the CC licenses made it more amenable to databases, but I'll have to do a little more digging to see if my memory is serving me correctly...