Falkvinge explicitly said above that it doesn't matter whether or not the entity is commercial.
The analogy with the postal service made earlier was actually quite apt.
Cheers, Rick
The line between "aiding file sharing" and "file sharing is their business model" is also very, very questionable. We all saw what happened to Mininova when they stopped "aiding".
TPB could easily run without ads. In my mind adding ads to something should generally not affect legality.
A guy who prints DVDs with movies on them and sells them on the street is a commercial pirate. A guy that takes DVDs someone else made and brings them to people is a courier. It's not a very complicated distinction.
If it is legal for you to download a file and burn it, it should be legal for you to hire someone else to do that for you.
On one hand, it might be legal, deciding the agency is in the person submitting the link and the other person is only automatically shoving some bits around.
On the other hand, you might decide that that's not a service that can legitimately be paid for. Some things can't be outsourced. I think right now that it's legal to 3d print a rifle but it's not legal to have someone else print it for you (but I'm having trouble finding references).
Either way, the intent of the law matters, and it's possible to outlaw commercial enterprises based around piracy but not individuals' actions. One method might be to limit the number of 'uploads' to a number like 10.
The commercial nature of the site affects whether it falls under non-commercial file sharing the OP would like to see legalized of course, in which case it changes the argument from "legalize non-commercial file sharing" to "legalize commercial piracy".