There was an educationalist in the 1920's in the UK called Thorold Coade who believed that all human beings are fundamentally motivated by 2 urges (he called them 'spiritual' urges, but not in a religious sense):
1. Creating - building a product, service, even self-creating one's own career and talents.
2. Serving - providing what you have created in service to others.
I think (1) equates roughly to Autonomy and Mastery, and (2) equates very closely to Purpose.
I believe that the popularity of open-source software and its development can be easily explained by either Pink's or Coade's theories. That is, autonomous creation away from corporate scrutiny, and close contact with end-users who provide feedback on the product/service you are providing for them.