This site holds all blitwizard downloads you might be interested in, including the source code. Simply pick the package for your platform and you're set.
Please note blitwizard is still unstable and unfinished, so expect some breakage. It isn't unusable, but it still has the one or other notable bug or issue. Check ISSUES.txt for the most obvious problems.
This is most likely what you want if you want to start using blitwizard right now.
Linux: blitwizard 0.3 Linux binary (.zip) (alternatively, take the source code package below)
Mac OS X: blitwizard 0.3 Mac OS X binary (.zip)
Android: for Android development, please obtain the source package and prepare a Linux machine (you can also do so in a VM).
On Windows, you can probably make an Android release work too, but it isn't officially supported and you'd make some hacks/changes here and there - so get a Linux somewhere, it's free!
Stable (used for the binary packages above): blitwizard 0.3 source code package (.zip)
Bleeding edge development code: Head over to GitHub!
FFmpeg is a library which, if present, allows blitwizard to play many more additional audio formats. FFmpeg is NOT provided or shipped with blitwizard, but many other applications installed on your PC might come with it (e.g. Steam) from where blitwizard will attempt to load it.
Technically, you can also ship the FFmpeg library with your blitwizard game. However, it seems to me the legal situation of doing that is complicated (FFmpeg implements patented audio technology), therefore you should be careful about that.