1) a member of the dev team posts changes to mafia source code, but not changing so much as to cause a full release, and perhaps introducing unforeseen complications
2) a kindhearted person compiles this new code as a .jar file on a roughly daily basis (assuming any changes have been posted, and the person doing the compiling has the time and gumption to do so)
3) said person makes this interstitial "release" available to the public and someone like you downloads it, knowing full well that it is not a vetted full-release.
4) repeat for duration dev team is interested in continuing developing the project