Signups can happen now. Once October starts you have 72 hours to log your first assignment. After that, it's 72 hours maximum between logs, as explained in the pinned post with my name on it.

At least, I'm pretty sure that's how it works. It's been about 25 years since last October, and my memory's shot. Either way, it's definitely safe to sign up now, which is why B opened signups.