This is a myth. Microsoft bought a symbolic amount of stock. At the time Apple had over a billion dollars of cash in the bank. Microsoft was making over $300M a year in revenue from the Office product on the Mac platform, so it was in their best interest to keep up development. The only reason they were going to stop was to strong-arm Apple.
Back then Apple wasn't in great shape, running at a marginal loss or profit, but other companies at the time, like Compaq, were bleeding hundreds of millions of dollars in losses per quarter.