Author here.
Somebody did set up a website somewhere that allowed users to see if their private key was in the "database". It would jump them to the correct page, and, steal their private key in the process.
I didn't like them potentially stealing my revenue, so I implemented this feature myself. The pluses beside the private key are permalinks.
For example: http://directory.io/warning:understand-how-this-works!/5HpHa...
That's the private key in Bitcoin's importprivkey format.
I purposely didn't add a search box and named the URL's path to discourage its use.
(I don't actually check the logs)