Filesharing legality (not ethics!)?

Is it true that it is only a violation of copyright law to upload copyrighted files and legal to download them?

What if you have purchased something, and then you download a copy as a backup?

I'm sorry, you're not legally permitted to download something you own so as to have a backup copy. You can make your own backup copy, provided you don't then make that copy available to others. The difference is that if you make a copy of something you own, you're using your own property for space-shifting purposes. If you download someone else's copy, you're making an illegal copy, even if it is a copy of something you already own. It may seem bizarre, but it's the law.

It is not legal to download or upload copyrighted files unless you have permission of the copyright owner.

You asked: "What if you have purchased something, and then you download a copy as a backup?" - This again depends on the agreement you have with the copyright owner. The terms and conditions of the purchase should be spelled out.

The legality of downloading is questionable. But you're unlikely to be sued or anything for downloading, as you are permitted a backup copy of anything you buy.

Uploading, on the other hand, is 100% illegal, and you can be sued. All I got was my internet shut off for a day and I had to sign a form promissing that I wouldn't share that file again. But then that was from the movie people, not the music people.