"Sharing knowledge in the business world, never. That's a great way to lose a job."

I think that depends on the role and the organization.

Generally organizations do not like to loose valued individual contributors unless the organization is somehow pathological (I know those exists).

A programmer that delivers value is always worth more than his or her paycheck. If you can dump his load to a more junior dev then that's great, there are other, more important things always that need doing. That is, if the business is growing.