Got an email from the Diaspora team, here are some excerpts:
Thanks again for your interest in joining the Diaspora* community, and for your patience. We’re working on getting your invite out to you as quickly as possible, and we’re still committed to getting it to you by the end of October.
Diaspora*'s distributed design is a huge part of it. Like the Internet itself, Diaspora* isn't housed in any one place, and it's not controlled by any one entity (including us). We've created software that lets you set up and run your own social network on your own "pod" (or server) and connect your network to the larger Diaspora* ecosystem. You can have a pod all to yourself, or one for just you and your friends, or your family, giving you complete ownership and control over your personal social information (including your identity, your posts, and your photos) and how it’s all stored and shared.
Yet our distributed design means no big corporation will ever control Diaspora*. Diaspora* will never sell your social life to advertisers, and you won’t have to conform to someone’s arbitrary rules or look over your shoulder before you speak.
If you are interested in Diaspora, you can sign up here.