Software interrelationships have an impact on the quality and evolution of software projects and are therefore important to development and maintenance. Package management and build systems result in software ecosystems that usually are syntactically and semantically incompatible with each other, although the described software can overlap. There is currently no general way for querying software interrelationships across these different ecosystems. In this paper, we present our approach to combine and consequently query information about software interrelationships across different ecosystems. We propose an ontology for the semantic modeling of the relationships as linked data. Furthermore, we introduce a temporal storage and query model to handle inconsistencies between different data sources. By providing a scalable and extensible architecture to retrieve and process data from multiple repositories, we establish a foundation for ongoing research activities. We evaluated our approach by integrating the data of several ecosystems and demonstrated its usefulness by creating tools for vulnerability notification and license violation detection.