It's the same plug-in that Eli distributed with his wordpress installation in his cycle sites post, although I think he hacked it up a bit. Elliot Back was the original author and distributed it as a free plug-in on his blog. He removed it after getting complaints that it could be used as a spamming tool.

I have a couple versions, the original and it's update, another one with a markov script built in, and Eli's which sends a trackback automatically. I would think the original would be ok to distribute.