Now we have the fork of mambo.
One branch is mambo
http://www.mamboserver.com/
and the other branch is "the system formerly known as Mambo"
http://www.opensourcematters.org/

After the announcement made by the new mambo foundation the whole developper team wrote an open letter to the community, left the mambo project and started their own project.
Now, they are in the progress of organizing and finding a name for the new baby.

For millions of mambo users there is probably no problem. The whole devteam speaks with one voice and they want to develop the best CMS in the world (at the moment without a name )

The mambo foundation thinks in the same way (but without the power of developers).

So perhaps in a few weeks we have two competitors in the open source mambo world. Both have a big interest to be compatible to the old versions (Mambo 4.5.x)
The mambo foundation holds the name rights for mambo and the devteam and the community holds the know how.

Democracy can be interesting and creative!