As far as I'm aware of, HBO Showtime does not broadcast free-to-air from any satellite (C or Ku band) within the US. It does broadcast free-to-air to Northern Africa from Nilesat, but its footprint falls off sharply outside of this region and would be below the horizon from the US due to how far East it is.
Anyone picking up this channel within the US on a free-to-air box is most likely using a hacked firmware to unofficially decode the channels. This cannot be discussed about on this forum.
Unlike in Europe where most satellites carry a decent section of free-to-air channels, unfortunately most of the satellites the Dish network operates on don't even carry any FTA broadcasts that I know of, so if you're interested in picking up FTA broadcasts, have a look at Lyngsat's frequency charts and click a satellite position (e.g. 97Â°W) to see what it carries. Any channel names in the cream colour are FTA and the Tan colour channels are encrypted.
For a FTA system, I would also recommend getting a decent 60cm to 80cm satellite dish, as the dish the Dish Network uses is only really fit for its own service.