Here's what I think happened,
"Hey boss, I got a new job and I'll be leaving in a couple weeks."
"What? You can't do that! You're the only one that knows this program! You wrote it and we depend on you to support it!"
"Sorry man but this other job is too good to pass up."
"What do we do with the program then?"
"I don't care."
"I guess since we can't support it anymore, we'll just give it away for free. In the meantime, we'll get all the leads we can so we can market to everyone that downloads it."