Software as a service (SaaS) is a kind of cloud services that consumers can buy and use as a complete solution including a hardware infrastructure, a software platform, and a specific software running on it. SaaS brings a lot of benefits to the customers, i.e. hiding the costs for management and maintaining the execution environment. This service encapsulation is, however, one of the main causes for the problem of vendor lock-in, by which the software tightly depends on a software ecosystem created by the cloud service provider. The dependence on the vendor’s technology environment constrains the capacity of developers and limits the development of cloud applications. To overcome this problem, we propose a composable application model in which a cloud application is a composition of one or more software components that can be independently developed and deployed. Such components are provided via a cloud marketplace, establishing a new kind of cloud market with the participant of software developers, hence reducing the risk of vendor lock-in.