I'll post what I posted on the main boards here:
This play certainly fits the mold of interference, but it is definitely not boarding. There was also no intent, nor was it vicious, and I would argue it wasn't even reckless by Smith. It should have been 2 minutes at most, and if Borowiecki had handled himself properly going for that puck battle then this unfortunate accident doesn't even happen at all.
Borowiecki went in for a battle where he had to good footing at all. The contact happened while both players were still well inside the faceoff circle and the damage was done when he hit the back of his head on the boards beyond the goal line due to his own reckless momentum, poor footing, and willingness to engage.
Hit in faceoff circle:
Borowiecki looking right at Smith and leaning in to hit him as well to fight for the puck:
Borowiecki's completely off-balance footing prior to the hit: