People make offers and asks on Twitter all the time, and then the timeline eats them. Bulletin is one page where you can see them. Every notice is a tweet by a member of the archive, so nothing is posted on anyone’s behalf, and “answered” or “taken up” just counts public replies and quotes from other members. You put something up by tweeting it, starting with offer: or ask:, or by saying standing offer.
The standalone version is still up on GitHub Pages. The one people use now is inside Community Archive, behind a sign-in.