I think he killed his wife and Goldman. However, he went through our court/justice system and was found not guilty. He can't be tried for that crime again, which would be against the double jeopardy principle.
As for his parole, it was the right thing to do. The board cannot consider the murder trial or its verdict. If O.J. was a model citizen while in prison (and based on everything I've heard, he was), then he deserved to be paroled.
Actually, it's better for the Goldmans that he's out because they have a civil suit against him, and anything he makes, they can take. I heard this morning he receives $25,000 a month from his NFL pension. That's $300,000 annually, an amount that I'm pretty sure the Goldmans will go after.