When I double click jcmd.app, a get a dialog window with the heading "An error has occurred." See the log file /Users/kjeldaas/Download/jcommander-0.7.0/jcmd.app/Contents/MacOS/workspace/.metadat/.log
However, there is nothing in the workspace directory.
The .metadata directory is hidden so probably this is why you can't see it, but it definitely must be there. We really need the log file for clues about what is happening.
On a different note, have you tried running the 0.7.1 development version. If so, do you get the same error?
Robert