Daniel's blog has numerous tidbits on the platform's background, for the curious. At the moment the service is still kind of resource intensive, and you'll need Flash 9.0.115 and FF 2/3, IE 7/8 or Safari - Firefox 3 beta 4 might help. They made most of the games, and implemented an 'attention-based' currency that can be obtained from playing those games. Most of the avatars, furniture, and pets, though, have already come from the community. Plenty more details (esp. those for the technically inclined) are available at the Whirled Wiki.
A few thoughts on the project below.
This thing already shows amazing promise! Your little tofu starting avatar is brilliant, there's a ton of amazing alternate avatars in the shops, and many many many room customization options to purchase. The games are a really slick way to make money, and I am floored by how much fun Brawler Whirled is. Ian (of Mac Hall fame) is a great artist, and his work is showcased v. well here. There are a lot of game world platforms coming at us in the near future, and if this is just what we can expect at the start I'd say we're in for a wild ride. Congrats to Three Rings!