The Nasa page says

Maybe one of your answers is right and this led to an upwards re-evaluation of the input energy needed to explain the thermal output from Ganymede. If tidal effects from forced libration were insufficient, then researchers may have needed to opt for a radioactive source from a long-lived radioactive isotope.

Generalising, they would then find that very long-term radioactivity solves a similar problem for Ceres. The timing of the Ganymede conference would thus be very astute by bringing energy balance into the limelight. NASA might even get lucky by discovering another thermal imbalance around Pluto this summer.

Whatever, their argument would be to suggest that other cold worlds far from their star (and even orphan planets) would also benefit from a similar heating mechanism.

And so to a paradigm change for habitability without a habitability zone. Well, its just an idea. We'll see tomorrow !