I wonder what you would have done?given that the glider pilot stated he did not see the other aircraft we can assume that he didn't land towards it on purpose,he is in sink and going down,probably somewhat nervous at the thought of landing out and in a high workload situation.Are you really saying he should not enter the atz when the runway is under him? He can't open up and go-around.
The student,in the same situation handled it well in my opinion.But I would not want to have been in iether position and certainly don't feel comfortable apportioning blame!