the pilot involved in this situation is definately not at fault! i can assure you all he is an IFR driver (with about 6000 hrs!!) so there is no issue with respect to the aircraft punching up through cloud.
There certainly is an issue if the aircraft is not certified IFR category and no IFR flight plan lodged. Many of the jump aircraft with door off approval have a VFR only restriction in the flight manual. Very few of those same aircraft are ever maintained IFR cat.
I seem to recall at some stage that PJE ops, unless specific approval otherwise was given, were to be conducted under VFR. Not sure whether this was covered under a relevant CAR or within the APF operations manual. Can anyone out there clarify that point?