Perhaps the developer of this software should consider changing its name; the reason being that there is ALREADY software available for Mac OS X called Jack. It is in fact an audio server -- in development since 2004 -- similar to Soundflower.
Having the same name as the Jack audio server is very confusing. When I saw this listing today here on MacUpdate, I automatically assumed that it was for an update for the Jack audio server.
You can learn more about the original Jack for OS X at the following URLs: