Ghostbusters 3 won't happen without Bill Murray

According to Deadline, Bill Murray has receieved the recently completed script for Ghostbusters 3. Sony won't shell out the $150 million unless he is onboard. Some speculate Murray's reluctance is due to the script for Ghostbusters 2. And there is some logic to that. I mean, if he hated the franchise, why would he come back to do the voice characterization for the video game, or show up at last year's scream awards in the uniform?