Apache DataFusion is an extensible query engine written in Rust that uses Apache Arrow as its in-memory format. It provides SQL and DataFrame APIs and reads CSV, Parquet, JSON and Avro files, with a query planner and a multi-threaded, streaming execution engine. Developers use it to build data platforms, query engines and analytical tools; related subprojects offer Python and Java bindings and a Spark accelerator. DataFusion is a library, so it runs wherever the software that embeds it runs.
DataFusion is licensed under the Apache License 2.0 and maintained by the Apache Software Foundation, a US non-profit that manages the project's trademark and governance. The project is open source and self-hosted: no vendor cloud service is involved, and data stays with the organisation running the software. For a European organisation, the sovereignty question therefore concerns the infrastructure and the teams that build on the engine, while the US foundation remains the body that governs the code.