Those are official releases, having their own unique version number. They come split in four packages and are available as *.tar.gz archives. The *.tar.gz archives are for usable on Windows, too. Most archivers can handle them just fine.
What do you need to download? As said already, the releases are split into four packages:
To download the current (and earlier) releases, please go to the last releases page or directly to the download page at SourceForge.net.
If you are a Gentoo user, you have an easy way out:
Thanks to the fine folks of the Gentoo "web-apps" team!
If you want to, you can of course check out the current code from the CVS repository directly. This will make it possible to follow updates closely (be aware of the time lag SourceForge.net has with anonymous CVS, though).
We assume that you have basic knowledge about CVS, so we just point you to the project CVS docs at SourceForge.net. Use 'mgw' as modulename!