My server isn't designed to do the kind of task that JSONP requires it to do, esp in service of apps that make lots of calls to the server each minute (for each user). I just spent a few weeks cleaning up all kinds of things like this, so I'm not willing to keep hosting it.
To give you an idea of what it's doing to the server it's running on, here's what its performance monitor graph looks like now. Obviously that's not workable.
So, I've modified my app to produce a static file that I can serve without this cost that calls a routine in your page called onGetRiverStream. You don't get the flexibility to say what routine you want me to call, but you can have that routine call the routine you want.
The static file it's generated from is still available, and you can have your own JSONP handler work with it if you like. Or if you really want to be community-minded, you could let other developers access it as well.
Update: Here's what the performance monitor graph looks like after I switched to this new policy.