Here at Lime Technology we manage two release branches: stable and next.  The stable branch is for those users who want better tested, though less frequent releases.  The next branch is where all new development takes place.   If you are running a 6.4 stable release, go to the Tools/UpdateOS page and select the Next branch.  If you are running an earlier stable release, to get on the next release branch, install this plugin: https://s3.amazonaws.com/dnld.lime-technology.com/next/un