License should be an existing standard

Open Definition lists a number of suitable open licenses for data (https://opendefinition.org/licenses/). The current license language clearly requires attribution. Less clear is whether it requires share-alike (that any derivative data must be under the terms of the same or compatible license). Top choices include:

• Attribution
  • Creative Commons Attribution 4.0 (CC-BY-4.0)
  • Open Data Commons Attribution License (ODC-BY)
• Attribution & Share-alike
  • Creative Commons Attribution Share-Alike 4.0 (CC-BY-SA-4.0)
  • Open Data Commons Open Database License (ODbL)