If I'm reading this correctly, the fundamental difference between a "Libre Puro License" and say CC-BY-SA would be no requirement for attribution under a "Libre Puro License"?
It seems that there is one-way compatibility, i.e. Libre Puro ==> to compatible license, but not the other way around?
You'll need to think about how to resolve the attribution issue. From recollection, the legal code of a CC license through written permission, can remove the requirement for attribution under a CC-License, so the Libre Puro legal code would need to provide for this one-way compatibility.
(I'm speaking under correction here -- so you'll need to check up on this.)