Interest around cloud computing has been growing quite rapidly during the past few years, and the model of cloud computing is evolving into an indispensable component of innovation strategy across the software industry. We are witnessing a paradigm shift that will have a profound impact on software platforms and ecosystems and will give rise to new forms of software co-development. In this paper we make a first attempt to discuss the evolution of the relationship between software co-development, platforms and ecosystems in the era of cloud computing, and the role of cloud application platforms. We present the case of a cloud application platform designed to support advanced forms of software co-development, and to foster the emergence of a novel type of software ecosystem. As demonstrated, cloud application platforms can be designed in a way that facilitates the emergence of new forms of hierarchical cloud-centric software ecosystems.