Nah, seriously, maybe something along the lines of "Libre Derivatives". Depending on the audience, the "libre" word could be commonly understood in this sense.
Maybe "Libre Remixes"? I'm not sure if that word matches the kind of "derivative works" you have there (or at least most of them).
My 2 cents =)
P.S.- "Copylefties"? xD
EDIT: Interesting. Your edit with "Remixes" came at about the same time as my comment =)