Musicbrainz allows bootlegs, if they're "notable" enough.
That is a very grey area, and open to interpretation. But it definitely means that just because something is only available online doesn't disqualify it.
In the case of the Indie/Rock Playlist torrent series I've actually heard of them before, so I would say they're pretty notable.
Personally I wouldn't worry about it so much, MusicBrainz hides bootleg releases from view for a reason, and we don't allow linking to illegal downloads. One thing I definitely would take issue with though is the misrepresentation of bootlegs - not being honest about the source or passing them off as official.