For playing Impulse Tracker Modules you need one of the following. Impulse Tracker itself, MikIT or WinAmp.
These songs are either composed with Scream Tracker 3 or Impulse Tracker. I can't remember which are composed with Scream Tracker which with Impulse Tracker and which are composed by using both. They are anyway saved in S3M-format, so you can use even Scream Tracker or Cubic Player or many other players to play these songs though I would still recommend Impulse Tracker.