Rob Rubin, vice president for engineering at edX gives some context:
“We are an open source initiative because we think the community can help us dramatically improve the product, and we expect that there are teams who can collaborate with us to experiment with and evolve the teaching and learning experience. We look forward to the impact that expanding the edX platform developer community will have in the future.”
Going open source is a smart move for edX. It will help edX further differentiate itself from Coursera and Udacity as the clear non-profit choice. It will also help edX more rapidly improve its platform both by bringing in outside collaborators and opening the way for the platform to integrate existing 3rd party apps. Finally, it will also allow universities and other institutions to experiment and become comfortable with edX before fully committing to joining the consortium.