From ALT Linux Wiki
Sisyphus is quite dynamic project which makes it hard to schedule and perform releases based on it. To overcome this system of branches was invented: Sisyphus is regularely literally branched creating a new repository which is then stabilized for a several months. Resulting repository is called a branch and used as a basis for distributives and solutions. After stabilization branches only incorporate security and critical feature fixes.
Every branch is an APT repository containing source and binary RPM packages in branch.
branch/4.0 (Fall 2007)
Base of ALT Linux 4.0 distributions.
branch/4.1 (Spring 2008)
Base of ALT Linux 4.1.