The picture seems pretty clear to me, that Russian rebels shot down the plane with the BUK missiles they already admitted they had, and were negligent in doing so.
In addition, I would put about 20% of the blame on the Kiev government. It was clear from the 29th June, when the rebels admitted having access to BUK missiles that the airspace should have been closed. The rebels were taking pot shots at a sky that almost inevitably would result in a plane going down. So why was airspace not closed? It's ludicrous the 32000 ft safety limit when the missiles known to be available to the rebels had a vertical limit of 25km and a 95% kill efficacy (according to Wiki). The Kiev government was also either negligent or cynically deliberate.
To me it is analogous to having a school run bisecting a military shooting range. Who is at fault? The school for organising the daily school run, the parents for letting it happen, or the soldiers who continue with their practice pot shots, without checking what targets they were shooting at? All three I would say.