It doesn't seem to be returning any rows, no matter what options I pass.
so.. yeah... I've had problems too, it'd be because of npmjs.org API instability as they reorganise basically everything about it. If you leave it running you'll probably find them coming in bursts but I'm not sure why yet and haven't had time to figure it out.
I think they might've changed the format for the keys. This seems to assume ISO8601 dates, while npm-tweets seems to use number of milliseconds since the unix epoch.
I'm going to add you as a repo collab in case you find the time to sort this out sooner than I do. I'm more than happy to take contributions on this.
in addition to the PR above I use these settings in browserify-cdn now and it works:
refreshRate: 2 * 60 * 1000,
should be good to go now I believe @ForbesLindesay, could you try it out and close this issue if it's working for you now?