Cyber-physical systems that interact with each other and form groups to achieve joint goals, are referred to as collaborative cyber-physical systems. They are exposed to highly dynamic and open contexts only partly known at design time. While model-based systems engineering already helped overcome various challenges regarding the development of conventional cyber-physical systems, challenges remain with respect to highly collaborative systems. This paper proposes an approach for modeling the context of collaborative cyber-physical systems and generating ontologies that they can use at runtime to communicate with each other and perform context-related reasoning. To account for the broad domain scope of such systems and unforeseeable future applications, the approach is not limited to a static set of prescribed ontological concepts. Instead, it facilitates the incorporation of custom concepts to meet the individual requirements of a broad spectrum of development projects concerned with collaborative cyber-physical systems.