"The site doesn’t have any current plans to pay contributors, but to help incentivize users to write high-quality courses, Codecademy aims to provide significant exposure to the best lesson creators."

I know Ruby very well (programming with it since 2006) and I have been professionally trained as a teacher. Yet "significant exposure" is not an incentive for me. I already have enough exposure to get the programming gigs that I want. My incentives would either be (1) money or (2) the joy of teaching. Since I have hardly any free time, my only incentive would be (1) money.