It's natural to look for someone to blame. Should we lay the blame on MIT? If they had called off an overzealous D.A. from throwing the book at him, he might be alive today. Why not blame the D.A.? Or JSTOR? In any case, aiding in prosecution did not cause his death directly.
The decision to commit suicide was ultimately his own. Of all the options he had available to him, he consciously chose that option. I'm reminded of a quote by Viktor Frankl:
"Forces beyond your control can take away everything you possess except one thing, your freedom to choose how you will respond to the situation."
Aaron had the power to choose right until his last choice. Why do some people survive terrible hardships, and others don't?
According to his close friends' personal accounts, Aaron suffered from suicidal thoughts and depression for many years. Long before the JSTOR case, and long before MIT ever got involved. As long as we're speculating about things we can't know for sure, I'm guessing depression was really to blame for his suicide. That won't satisfy everyone, since it doesn't give them a powerful organization to rage against. But reality doesn't always work that way.