The Mambo project launched its own forge last year (see: https://sourceforge.net/forum/forum.php?forum_id=746897/&abmode=1 for the announcement).
The new forge can be found at http://mambo-code.org. It provides hosting for Mambo official releases and open source 3rd party Mambo extensions. No more official releases will be added to Sourceforge.net at this time. The official Mambo project code page is now http://mambo-code.org/gf/project/mambo/.
Please ensure you visit the Mambo forge for the latest releases.