Change license options

[prabhant]

Since you cannot copyright tabular data, make only CC0 and public domain license options on tabular datasets uploaded to OpenML.
And allow CCBY for Images and other high-dimensional datasets.

[joaquinvanschoren]

Can you elaborate on this, please? Is CC-BY forbidden for tabular data? It would be great if we could point our users to a better explanation about this.

[joaquinvanschoren]

Also, does that mean that tabular data should always be CC0, not 'public domain mark'? If it cannot be copyrighted, the 'no known copyright' mark doesn't make much sense?