GlusterFS is likely to implement S3 storage according to this forum post

Apple launches draws press. If Apple were to release something spectacular at the same time, that would draw a lot of press, downplaying the Vista release. Leopard will be spectacular, and so will iLife '07 and iWork '07 based on Leopard. To me it would make perfect sense for Apple to release all these three packages at the Vista launch date. I would ...