This research introduces an approach for building open-source software ecosystems (SECO) aimed at territorial monitoring. At the core of this approach is the semantic integration of diverse and continuously expanding data sources, including satellite imagery and ground-based sensors. This integration delivers a cohesive and adaptable data stream that can inform territorial monitoring. The SECOs developed through the proposed approach enable the encoding of metrics to support several applications, aiming for the automated generation of KPI-driven, persona-based insights and dashboards tailored for a wide range of stakeholders. To showcase our approach, we identified a use case in which air quality, temperature, and walkability are the quality of life (QoL) metrics used as KPIs. Applying software engineering principles and the proposed approach, the resulting SECO consists of a persona-based UI/UX (i.e., supporting urban planners, public health officials, and citizens) capable to integrate agent-based and predictive models with Geographic Information Systems (GIS).