There's been some talk for a while now about the idea of putting together a properly distributed imageboard, and there have been some efforts made towards that end. However, in my view the current efforts still have a number of weak points that leave them vulnerable to targeted attacks knocking them offline. NNTPchan for instance is cool, but the way it's put together DDoSing a (relatively) small number of nodes is still sufficient to take the federation down.
For the past year now I have been slowly working on an IPFS-based federated imageboard software package. It's still in a very early state, and I was hoping to let it sit until IPFS developed a little more, but recent events have made it clear that the noose is already starting to tighten now so out the door it goes.
Github: https://github.com/smugdev/smugboard
Working instance: http://localhost:8080/ipns/client.smugchan.org/#Qmf9QKURJVU53mzmysAFAR3mj48dLXqS2rNpq2o41EugcV/tech
(You need a running go-ipfs daemon set up as per https://github.com/smugdev/smugboard#usage to actually access it)
This is Smugboard, an imageboard package with a fully distributed content layer and a maximally decentralized control layer. It is composed of 5 separate server packages handling different aspects of posting and moderation, and a client-side renderer. Each thread and board takes the form of an append-only log hosted via IPFS, with moderation taking the form of a client-side filter. Users can choose to toggle specific mods on or off (soon - UI not yet complete).
As noted the federation is composed of a series of append-only logs, and these are published directly within IPFS. A proper UI for this isn't done yet, but it will be possible to fork any board or thread from its current state, or from any previous state, at any time. In the event of a board going offline, the board's state still exists within the IPFS network and as long as a copy still exists in any user's cache the board will still be retrievable (in a read-only state), and can be forked and restarted from that state or any of its previous states by any other user. As the content layer works like a bittorrent swarm, the board will paradoxically load faster the more people use it.
Again, this software is still very much a prototype so expect bugs and fun, there's still plenty that needs implementing and contributions are welcome.