Official source code of FreeCAD, a free and opensource multiplatform 3D parametric modeler.

Free and Open Source Reverse Engineering Platform powered by rizin

Cross-platform, graphics API agnostic, "Bring Your Own Engine/Framework" style rendering library.

TreeSheets : Free Form Data Organizer (see strlen.com/treesheets)

Very customizable imageboard/booru downloader with powerful filenaming features.

A Flipper Zero clone, but cheapest, DIY and simply Open Source, made with Arduino IDE

100kHz to 6GHz 2 port USB based VNA

A Spotify Connect player targeting, but not limited to embedded devices (ESP32).

EmberGL - 2D/3D graphics library featuring a tiled software rasterizer.

Anotter OSHW environment sensor hub, focussed on Sensirion SEN055/SEN05x sensors, featuring a prometheus-exporter.

LAEMP-Panel is a Zigbee controllable (e.g. philips hue) RGBY + W spot.