Yosef Greenberg says that it is in "Copying Music Is Not Wrong!"
What is most astounding about this ignorant assertion is his implication that if halacha theoretically permits something that civil law prohibits, and there is no compelling reason not to follow the civil law, it is nevertheless permissible because dina d'malchusa is irrelevant..
This post is ignorant, because many if not most recognized poskim do maintain that dina demalchusa is quite relevant in the USA today, jaywalkers notwithstanding, and many poskim would also note obvious external issues like chillul Hashem, eiva, etc. that might well apply. Only a handful of poskim maintain that one is permitted to copy software or music for others, and few well-known poskim have said so on the record.
Incidentally, these poskim also hold that one may cheat on their taxes and other similar views. Not exactly mainstream, in other words.
Go ahead Yosef, post the links to the pirate sites you mention. (Do you run one yourself?) If you really believe what you write, have the guts to stand behind it.