I have a friend who was just accepted to JSP so I can tell you that they do provide something like typical grad school funding for the PhD (although from what I can tell, maybe slightly less than typical political science / sociology PhD funding). For those who decide to do the joint PhD-JD route via JSP, I think they receive a significant discount on law school tuition but not a full remition.
Would you care to share yours?
Here's mine:
22k/year plus 2k each summer (total = 24k/year).
First year fellowship. 5th year, completion fellowship (assuming normative time).
Years 2-4, GSI/GSR requirements.