IMHO it just seems like something they created to cover their own ass. I wouldn't be afraid of MD taking down your content themselves without a DMCA notice from the copyright holder (which is, historically, pretty rare). If you are worried about being sued or something, I guess it can't be helped. I doubt most distribution sites make you claim you are the copyright holder, which I assume would make you culpable for any supposed damages if the copyright holder tried to sue (which I do not think has ever happened to a scanslator, but do not quote me on that).
Anyway, if you are still intent on leaving, thank you for the translations, and good luck.
MD-Style Cover-My-Ass Note: None of this is legal advice.