I’ve very recently started contributing to the nixpkgs repository of packages,
which contains all the packages you can install from the Nix package manager. My
contributions are fairly modest: I help fix R packages that need some tweaking
to make them successfully build for Nix. Most of these fixes are very simple
one-liners.
Most users of any free and open source tool rarely contribute to the development of this tool: I don’t think it is due to lack of skills …