A Sourceforge update email includes that they're updating their project ranking formula. They write:
The OLD project ranking formula was: log (3 * # of forum posts for that week) + log (4 * # of tasks ftw) + log (3 * # bugs ftw) + log (10 * patches ftw) + log (5 * tracker items ftw) + log (# commits to CVS ftw) + log (5 * # file releases ftw) + log (.3 * # downloads ftw)
I would imagine those constants (3, 4, 10, 5, .3) were intended to weight these different numbers differently. Unfortunately, log(a*b) is equal to log(a) + log(b), so all of those constants can be pulled out into one term that's constant across all projects. Since the score is used only for an ordering, the constant term can be ignored, which means that each of these variables is ultimately weighted equally.