If you are running a torrent site with "links" (.torrent files available) it's illegal. Torrent site is not hosting any videos, just links to them. This is exactly the same with popcorn time because they have providers in their code base. In case of the torrent site interface is a website, in case of popcorn time it's an desktop application. If they would remove providers (torrent sites/trackers with illegal content) from their code then DMCA would be invalid.