This task is about legal aspects only. For technical implementation, see T200968 and T155290 instead.
All data and metadata provided on UNdata’s website are available free of charge and may be copied freely, duplicated and further distributed provided that UNdata is cited as the reference.
Does this imply that the data is CC0 because we can copy it, mark it as CC0, but since we are providing a link to the source, we are ok? Also, it does not say that the derivative works (e.g. a visualization of that data like a graph) needs to cite the source (although it could of course). I suspect that this is different, but since its not one of the well defined licenses, e.g. CC-BY, and simply because it's a legal matter, I would like legal to comment how we should proceed with this?
There is also another discussion about using more restrictive licensing here.