Donation. It's not a business, so much as a group of geeks who wanted to bring back the heyday of GR. You can Flattr or bitcoin I think, and they've managed to

Donation. It's not a business, so much as a group of geeks who wanted to bring back the heyday of GR. You can Flattr or bitcoin I think, and they've managed to keep a steady influx of donations thus far. By definition, it's easy to maintain since the goal of the project is "no additional features". So, the main cost is server load, which these days is easy enough to manage.