Yeah, it's getting colder outside on the global scale. Just look out the window every winter. It's all the proof I need. This winter the snow excess here was a football field-size snowflake. Those damn alarmists don't know what they're saying, let's just wait and see how wrong they are.

Well played, sir, well played

How can it be already registered without confirmation e-mail?

I think I went on with the Google hype about Wave, but I could see in it a replacement for current usage of e-mail (document collaboration, discussion threads, file transfer) as a lot of people abuse the reply with history feature of mail.
Because it wanted to replace e-mail it tried the federated approach for inter-server communication. Having servers of different ownership communicate freely would have provided migration or further along the way interconnection with social media (think about migrating a Facebook group or a forum thread to a Wave conversation).
Also today we use a mix of realtime/instant (chat) and offline/persistent (e-mail) communication. Isn't it time that somebody would try to invent a product offering both types of communication in the same package?

Pardon me, but if you look closer, in that github there isn't any Rizzoma server, just some gadgets.
There are no updates on Rizzoma core since early this year (I think January) and they didn't choose a license for it.
I saw that they are still working on some gadgets, and their server performs quite well, but that is a sign that developer involvement decreased once they reached a stable base.

Just to solve some of the unknowns of the thread:
1) between servers, Wave federation uses XMPP with some mumbo-jumbo/magic messages and as such it can be hosted (and interconnected) in a mesh, so yes it is medium independent.
2) between server and client Wave uses HTTP with websocket.
3) Wave is not a moving target as the protocol is no longer developed at high pace, if at all. The "Wave in a box" platform is still being incubated by Apache (waiting to get stable an attract developers).
4) I personally participated to the beta and I liked it.The potential to couple cooperative editing with the replay feature is huge on a lot of use-cases. It just gave you too many tools editing and little automated housekeeping so it ended a lot messier than e-mail conversations. Also, Google version of Wave was awful as a workflow. Rizzoma looks way better.

Communities could start asking members or FOSS users to donate CPU cycles for a buildbot, a BOINC [boinc.berkely.edu] computation project or just to mine some donations. Just a thought.

FTFY.