With the development of information and communication technologies and Internet of things, the open-platform strategy has come into the spotlight. Opening a platform allows external firms or individuals to enter the platform ecosystem without any restrictions. A platform connects diverse products and services, and thus the aim of this study is to simultaneously investigate the effect of platform openness on multiple groups of products and services from an ecosystem perspective. This study specifically focuses on the manner in which Android's openness to both applications and devices influences the intentions of application developers to continuously participate in Android platform through the structural equation modeling. First, openness to applications directly influences the participation intention of application developers as well as the user base of the platform. An increased user base leads to the enhanced participation intention of application developers through indirect network effects. Second, openness to devices contributes to increasing the user base, which in turn, positively influences the intention of application developers. Openness to a device also incurs coordination costs between applications and devices, and this has a partially negative effect on the participation of application developers. The contributions of the study include presenting an analytical model that offers a comprehensive understanding of the mechanisms of platform openness to external developers.