I was looking the Pandora FMS stats of last year and I said "Why not use Pandora FMS to watch this numbers for me?"
In this way, I created a really simple plugin (in PHP, to be executed from command line) to get the number of downloads of a project in Sourceforge
between two dates.
You can see this script here
Using it like a remote plugin in Pandora FMS, you can monitorize the downloads of one or more projects easily.