As others have mentioned AppleSeed for non-devs has been around for years. I've been testing major OSX releases since the end of 2008 for Snow Leopard - friend of a friend at Apple was looking for people to test exchange integration, IIRC.
I'm not sure this will give access to 10.10 seeds though - for the last couple of releases we've gotten redemption codes to install them initial seed - it's a separate application, not a software update.
I'm not sure this will give access to 10.10 seeds though - for the last couple of releases we've gotten redemption codes to install them initial seed - it's a separate application, not a software update.