[racket] running web app from DrRacket versus command line

I cloned the sample twitter app from the git repo
http://github.com/jeapostrophe/pltwitter.git and can run the app form
DrRacket v5.0.1.

If I try to run from the command line using "mzscheme -f main.ss",
nothing happens - no errors or warnings - I just get the unix system
prompt back.

Is there a file somewhere I should be looking at to understand what
I'm doing wrong?

Thanks,

Scott Hickey