There's no mention at all at that site about how they determined how popular something is.
How are you hoping to get an accurate answer here. Anybody can download the framework (and nobody publishes their download numbers), but a single download could result in any number of sites being produced or no sites being produced. Factor in subversion updates as well and you have no way of judging how many people are using the framework.
You'll find Django is more popular than the other frameworks amongst people subscribed to this list, I would guess. And get a different result if you asked on the TurboGears list.
Really, you're asking an question that cannot have a sensible answer unless you conducted a seriously unbiased survey (which you won't be able to do on any of the framework mailing lists). So perhaps you might want to rephrase the question. Why is this information important?