Topic: which version of cc by-sa does this blacklisted item use?

cataclysm-dda::hyperbola:31:[nonfree] uses CC BY-SA for software

cc by-sa 4.0 is gpl3 compatible. source: fsf licenses page i believe (also email with rms, who corrected me as i thought all cc licenses were gpl-incompatible except cc0.)

cc by-sa 4.0 is not gpl 2 compatible, and previous versions of cc by-sa may not be gpl compatible. but by-sa 4.0 and gpl 3 are. which at the very least, means cc by-sa 4.0 can be used as a free software license and isnt non-free (even if it is a stupid license choice for software.)