It's the revenue divided by the number of screens. The reason the average is high is that the number of screens has been limited to large cities with large "gay" male populations. The people who want to see this movie have to go to one of the few theaters in the country showing it. That's why revenue per screen is high. Of course by showing on a few screens to packed houses, the distributors do save money on making additional prints so there is lower cost associated with that revenue. I've noticed that while promos of the homo movie were played in my home town prior to a feature film, no theater in town has booked the movie. I'm guessing they were trying to reach potential viewers who would then see it in another city.
That is EXACLY what they are doing. This thing has only opened to about 300 theaters and BTW the per-screen average is dropping PRECIPITOUSLY (see http://www.the-numbers.com/movies/2005/BRKMT.php).
It was a cheap enough movie that it might break even (which is really a loss, since you have to have receipts about 3X a movie's cost just to break even) since a small number of ultra-liberals (and of course gays) will watch it, but that will be it.
If "success" = "getting nominated for awards" then Bareback Mountain might score. If "success" = "making money" it will be a dismal failure.