DuckDB is an analytical in-process SQL database management system

Apache Arrow is the universal columnar format and multi-language toolbox for fast data interchange and in-memory analytics

Dolphin is a GameCube / Wii emulator, allowing you to play games for these two platforms on PC with improvements.

Cap'n Proto serialization/RPC system - core tools and C++ library

A data visualization and analytics component, especially well-suited for large and/or streaming datasets.

Open source server for the FusionFall client

An example Flight SQL Server implementation - with DuckDB and SQLite back-ends.