We actually have a lot of people asking us to provide this kind of functionality for open-source projects. In a lot of cases, the projects have complex assembly requirements (like BGAs) that restrict self-assembly to the most capable makers. By making it really easy and affordable for people to order a single unit, they see it as an excellent way to spread their project to the world.
Our model is designed to support the business-side of electronics manufacturing and operations, and our intention is to be impartial to which marketplaces/how makers sell their products. Instead, focusing on enabling connections to those market places. This is why we have not chosen to create this sort of marketplace for our customers directly. (We are integrating with a lot of other popular platforms for makers/inventors that want to sell their designs later this year.)
I'd love to help you create this sort of integration, or to answer any questions you have - please feel free to reach out to me here, or at church at macrofab net. Our API documentation is also available here: https://factory.macrofab.com/apidoc/v2/