Alpha - contains pre-release versions currently available, if any. Do
not touch it with a bargepole unless you know what you're doing.

Beta - contains the latest version considered stable enough for public
testing.

Stable - contains the latest stable version considered ready for
production servers.

Old - is old unsupported versions.

Varients - are 3rd party varients of the offical code which include
specific features that they wanted to add.

The source file (.source.tar.gz) is always the most up-to-date.
Sometimes it takes a few days for the package maintainers to get round
to producing  the .deb/.rpm/.pkg files.

Be aware that only the source files are are made by the
DansGuardian author and all others are contributed.

The best thing is to grab the latest stable source and compile from
that.  It's easy, trust me!