I don't see them making any money from it and even if they do make it free people will still give this game "donations".
If Poxpoints is already making a few USD here, PoxNora itself is realistically speaking making quite a few more. So your assessment of them not making money of PD is likely wrong, I would imagine it still generating a few hunderd USD per month.
Honestly poxpoints kind of poached money from Devs of poxnora through 3rd party it doesn't really matter much
I'd be curious to see the stats behind that as I honestly think Poxpoints has increased revenue for PoxNora itself so far. But I obviously do not have the revenue statements of DoG.