The full and true story about what has happened to the well-known Mambo Open Source CMS is not known to me, nor am I that interested in investigating it. A simpler bit of information is that a significant number of the Mambo core dev team have now created the Open Source Matters (OSM) foundation, have rebranded Mambo as Joomla and are now developing and making releases based on a stable Mambo code snapshot.In an open letter to the community, the OSM team states:
"We, the development team, have serious concerns about the Mambo Foundation and its relationship to the community. We believe the future of Mambo should be controlled by the demands of its users and the abilities of its developers. The Mambo Foundation is designed to grant that control to Miro, a design that makes cooperation between the Foundation and the community impossible." Joomla is free, open-source, licensed as GNU GPL and all that good stuff. Its alive and kicking -- the OSM boys have so far made several releases, with v1.0 mapping directly to Mambo v22.214.171.124.
Their stated intention is to support backwards compatibility with Mambo 4.5 for the foreseeable future, however the they are certainly encouraging migration from Mambo to Joomla.
The developer community is now run on an instance of Source Forge, and as of this writing, there were over 5000 registered users and there had been over 15,000 downloads.
The project has energy and broad community support. Its good to see that the shake-up has turned into something positive and that the OSM team has taken a respectable and even inspirational stance. Good luck to them.