^ Correct. And the inability to specify different licenses for different parts is intentional; Having multiple licenses that people must follow for a single submission promotes incorrect adherence more than it promotes freedom. It is far less confusing to package separately licensed content in separate submissions. Even if you could license derivatives of CC-BY as CC0, it wouldn't be permitted on OGA because it inadvetently encourages users to fail to properly attribute assets.

Note that the original issue above is not about CC-BY-SA vs CC-BY. It was about CC-BY 3.0 vs CC-BY 4.0. Were you asking about the differences between version 3 and 4 of CC-BY?

Nice! Good find, Baŝto. That answers my question.

@Technopeasant: these are certainly adaptations, so if you'd still prefer CC-BY 4.0, you can change it back with the addition of specifying the original was CC-BY 3.0 in the attribution notice section.

Fabulous! I learned something today. I've always been curious about the divergence of gameplay vs the major and minor arcana. Thank you!

Nice! These are great. Thanks for sharing them :)

CC0 allows everything, including reselling and redistribution. Even of the assets by themselves. Would you be willing to omit the "but not resell or redistribute as assets" stipulation? This is not because people want to redistribute your assets by themselves. It's because saying "no reselling, no redistribution" creates a legal pitfall that basically prevents people from distributing them at all, even when it's only inside their games, even when the games are free. 

If you are not comfortable allowing that, it is your prerogative, but it means they can't be hosted on OGA. In the meantime, I must mark this as having a licensing issue to prevent people from using the assets in a way you may not approve of. Let me know what you decide or if you have questions.

EDIT: Fixed, thanks! :)