It seems my information was out of date. They used to have a total prohibition on it: "No ad is permitted to contain or link, whether directly or indirectly, to a site that contains software downloads, freeware, or shareware."

http://successfulsoftware.net/2008/01/23/facebook-dont-need-...

So this is great news, right?!? I mean, it's not even my business and I'm really excited for you. :D