Run your own server? From my understanding there is no server involved. It is peer to peer and peers find each other by using DHT. It's closed source though, so you have to take their word on that.
My understanding is that you don't need a tracker when using the DHT. I'm not sure what the bootstrap method is to find the initial peers to start accessing the DHT, but once you've found one peer, it's easy enough to find more. Feel free to correct me.
Thats nonsense. The clueless torrent news sites like to boast that you dont need a tracker for dht, just a 'bootstrap node'. Whick is exactly a tracker.
Its one simple node which address is hardcoded in the clients. So, it is a tracker, just not a full bittorrent tracker.
In principle this is not a problem in a peer to peer network as long as there are peers. You simply store the message encrypted on enough peers that are in the swarm.
It seems though that they store the message on the sender's device until the peer becomes available:
how do you think one client can find another? i hope you don't think it was a internet wide broadcast... :)