They offer cloud hosting (powered by Amazon). The IDE serves as a bait to get signups, since it makes it very easy to deploy on their service (single-click deployment). It's pretty decent, too. They have a free 15-day trial with 256gb ram and 5gb storage, and that one is only $10/month after the trial is over (down from $25). The others go from $49-$169.

I think they really have something here, if they had Ruby support I'd jump on it: it reminds me of Heroku (garden) when it was a web based Rails IDE, but this seems just a bit better performing, at least from my end.