Part e-mail, part forum, part bulletin board, part chat, part blog, part comment thread...
There's more information in this blog post, but the short history is that I created the original version of Bicker a little more than ten years ago as shrinkwrapped software for offices. I sold a few copies, but the company wasn't sustainable as I structured it and Ruby libraries had a flood of big security vulnerabilities, so I put that all aside to get a day job.
Today, I still see the need for a communications platform that encourages well-behaved conversations, so this is (will be) a modern re-implementation of Bicker, taking the same premise---communications where replies can only be inserted at punctuation marks and there is no "general" reply to something---and making it a completely-open project that can take advantage of more recent developments in the area.
I intend to document the development process and design decisions as I go, over on my blog. If you only want to read the posts about Bicker, there's a tag for that.