BoeingMEL - indeed. Not a lot one can say; once one cancels IFR one is legally VFR which means one must be in VMC (simply speaking, not flying in cloud). One cannot cancel IFR (legitimately) if one is actually in cloud.
The question is whether at the point of cancelling IFR the pilot was actually able to proceed to a normal visual approach and landing. I am assuming here that the information that he made the radio call to cancel IFR is in fact accurate; it if isn't then we are barking up the wrong tree entirely.
On an FAA license (or, indeed, almost any license issue by a country other than the UK) one can be legally VFR without seeing the ground, and it is possible that when cancelling IFR (which in this case had to be done not below 1505ft AMSL if on the VOR approach) he was in fact really VFR. I consider this very unlikely, looking at the weather, but nobody will ever know what the pilot saw.
It is also possible that he was visual with the airport when at 1500ft or even higher; this can happen because a ground observation of say OVC/BKN007 can be accurate for a scattered layer with that base but the pilot is actually flying under a higher layer (base say 2000ft) and can thus see the ground below, and if this higher layer is sufficiently thick and/or there is little sunlight above (true at this time of the year even at mid-day) the ground observer may write BKN007 only, whereas a more accurate observation would be BKN007 BKN020. I once got a bollocking from somebody on the ground (a well meaning friend) for flying such a DIY approach but actually I could see the ground all the time. However the baloon ascent data (sounding) from Vienna which is very close to the time of the crash and only 10-20nm away shows no layering whatsoever at that point, and the whole airmass appears (on the MSLP chart I saw at the time - unfortunately I cannot get it anymore) to be fairly uniform. Also, and to me most tellingly, the pilot would not have flown into the hill knowingly, and even if he was flying in slightly marginal visual conditions, a Jetprop can go up like a rocket when in a hurry: +3500fpm.
There are a few bits I don't get.
One is the LOAV tower man saying it was "fog" but the Metars for LOAV show ~ 5000m horizontal visibility which is a very long way from what I would call "fog". It is perfectly good VFR horizontal visibility. What isn't VFR of course is OVC006 if you are going to descend down through it...........
One is whether the pilot actually said on the radio that he was flying the VOR approach. I may have missed this.