Per my conversation with Mike, we might need to quickly remove the "+" at the end of the CC0-1.0+ license code, as it implies future versions of CC0, which might not make sense. We can quickly do it right after New Year's. Need an Legal opinion on how urgent this is. Codewise its very simple.
Or later version is superfluous for CC0-1.0, which has no conditions at all, let alone any pertinent to license versions. The "+" notation and "or (at your option) any later version" is advisable for A/L/GPLv2/3 because those licenses aren't compatible with later versions of themselves without such additional permission.