Well I wrote it because I needed a way for programs to announce what they were doing and have other subscribing programs react accordingly. The closest solution I found to this was http://xmpp.org/extensions/xep-0060.html, but that didn't seem implemented yet so I wrote the simplest thing that could work.

Cool. Seems like there should be some security to prevent abuse though, otherwise surely I could just add a ton of subscriptions to pages on a target site, and start getting your server to DoS them?

Perhaps have it look for an 'allow' file on the destination first, and if it's not there, don't send any further messages?

That's an interesting way to handle the auth problem, I'll look into it...