And even if Boxopus claimed to protect you like some VPNs do, unless they also encrypt the files before uploading them to Dropbox, wouldn't you still be at legal risk with Dropbox? Or are Dropbox contents automatically encrypted upon upload so that employees have no way of knowing what they contain?
As long as you're not sharing your Dropbox, it doesn't matter at point. Copyright Infringement is a crime of distribution (or more strictly speaking, reproduction), NOT possession.
In the US copyright includes the right to make copies. As an individual you do not have the right to freely make copies for yourself. That's reproduction, and is expected to get you in trouble. The idea that "it's legal to download, just not upload", is a defense that's been long been claimed, but to my knowledge, has never been tested in court.
To be fair, though, I believe they (the RIAA, MPAA) haven't tested that case either. Maybe they're not 100% sure either.
Now, in Canada? I believe private-use MUSIC downloading is legal. (Due to shenanigans involving the fine levied on blank media made for the purpose of burning music. Basically, Canadians already pay the fine for music piracy, so, they get to do it. That's my understanding.)
In the UK it's not legal to download, but the only damages are the costs of one copy of the item. Doing all the paperwork and filing all the legal stuff is time consuming and expensive, thus companies don't bother with it just to recoup £14 for a movie.
But if you're uploading then the costs are the cost of the media * number of people in the swarm. And going after those people has -they hope- a chilling effect, preventing people from doing it.
This is "civil law" (A UK lawyer probably knows the correct terminology.)
If you're infringing copyright as part of trade -selling bootleg DVDs on a market stall, for example- it becomes a criminal offence, and is enforced by police and trading standards officers.
I don't think it is that simple. I bet that you click-accept something like "By ordering this file, you state that you have the necessary permissions and you clear our asses of any responsibility" when ordering a file. And even if you don't, it's still you who ordered the torrent download (resulting in re-distribution to other clients), which (I believe) matters more than the fact that you're not the owner of the client box.
You didn't order Boxopus to upload anything back to other torrent users and they are the ones who have chosen to send you the data they received. Seems pretty obvious that they are participating in infringement regardless of what their ToS say. I hope they have some good lawyers on hand.