They're not an "arm" of J-PAL or a consultancy, they're an independent nonprofit founded by Karlan that runs the exact same type of evaluations as J-PAL with the exact same network of professors. So its basically a sister organization that is slightly different in that its a nonprofit rather than part of an academic organization. I believe this is by design since it allows them to circumvent the MIT logistical bureaucracy when necessary.
You know what is worse tha Jpal? IPA. Those guys are the consultancy arm of Jpal and they behave like sharks figthing to get the money.
ESTHER Duflo is affiliated with both JPAL & IPA; she got her sister, ANNIE, a fundraising job @ IPA.