Sephyn74, Copyright law is unique in that it allows the original holder to decide where & when they enforce their rights. If nirvana & the cure decided it wasn't worth it to pursue either case that's their decision & in no way diminishes their ability to sue the next person who tries it. That doesn't make it legal, nor will it protect someone if they do the same thing at some point in the future. and just as an FYI "Weird" Al gets permission from everyone of the artists whose songs he parodies.