Correct, but each mod has non-derivative parts from what I understand (Correct me if I am wrong in this, with examples I actually find this topic interesting). Some examples would be over half of EE2 (rings, etc), IC2 (cables and such), Buildcraft (engines and such), Enderstorage, there are plenty more examples. Each add a feature not based on Minecraft, add their own special artwork, etc. The way I read that, isn't derivative but full copyright?