Caioaf,
There's no policy requiring anyone to sign in to view the forums. In fact, we have 56 guests doing that right now. There has never been any restriction on people not signed in viewing the general forums. Posting - yes, you need to sign in. But viewing - nup.
Odds are it was popbably a transient glitch - there's no forum maintenance scheduled that I'm aware of, but these things can happen.
Titania42, we're welcoming enough to respect your wishes. Are you reporting the same issue Caioaf had? Caioaf, are you still having that problem? If so, can you try clearing your cache?
Worktroll, Ombidsman