FLOW3 is currently available as an alpha version which you can download directly from SourceForge.

Naturally, this version is not yet intended for production use unless you know what you're doing. However, we consider the published APIs as quite stable and are burning to see what apps you create with it!

The most recent development version of FLOW3 is available via SVN:

svn export https://svn.typo3.org/FLOW3/Distribution/trunk ./

Note: When browsing the above link via a web-browser it will seem mostly empty. This is caused by our use of svn:externals properties to tie packages together for the distribution. Make sure to actually check out the URL with a Subversion client of your choice to see the code.