Published in 2020, the European strategy for data sets the vision for Europe to become a leader in a data-driven society by establishing so-called common European data spaces in all strategic societal sectors. Data spaces are envisioned as sovereign, trustworthy and interoperable data sharing environments where data can fairly flow within and across actors, in full respect of European Union (EU) values to the benefit of European economy and society. The development of data spaces is accompanied by a set of horizontal legislative measures, including, among others, an Implementing Act on high-value datasets under the Open Data Directive that lays down a list of datasets (many of which being geospatial) that EU Member States public sector organisations are required to make available for free, under open access licenses, in machine-readable formats and via Application Programming Interfaces (APIs). The talk will describe the activities around open source geospatial software and open geospatial data that the European Commission’s Joint Research Centre (JRC) has performed to support the development of the common European Green Deal data space, focused on environmental data sharing and instrumental to address climate changes and environmental challenges in line with the top priority of Von der Leyen’s Commission 2019-2024. A key enabler to bring public data into this data space is the infrastructure setup for the EU INSPIRE Directive, which is technically coordinated, maintained and operated by the JRC. The INSPIRE Directive itself, together with the Directive on public access to environmental information, are currently subject of an impact assessment that might lead to a revision of the legal framework (GreenData4All initiative). This is accompanied by an overall modernisation of the technical infrastructure, increasingly based on open source software both at the Commission side (GeoNetwork for the INSPIRE Geoportal, ETF for the INSPIRE Reference Validator and Re3gistry for the INSPIRE Registry) and at the Member States side, where FOSS4G tools are the primary choice for both serving and consuming data. Thanks to a number of INSPIRE Good Practices promoted by the community, new standards and approaches for data encoding and sharing (e.g. based on OGC APIs) are bringing additional value to the INSPIRE stack. The same set of approaches ensures the full alignment and complementarity between INSPIRE and the Implementing Act on high-value datasets, thus positioning open source geospatial software as a true enabler for the Green Deal data space.