When you hear the term "open source," it's talking about any publicly accessible design that people are free to change and share as they please. It started with software development, with code that ...
It's actually easy to turn what you know about your local area into useful public info.
GitHub hosts powerful open source apps you can use daily, from Immich for photo backups and Upscayl for image upscaling to VERT for file conversion, BC Uninstaller for cleanup, Mole for Mac storage, ...