I contribute to Nextflow core (https://nf-co.re/) It's more of a collection of pipelines than traditional software, but there are users all around the world and a good community.

Most of the packages on bioconda (https://bioconda.github.io/) are open source. But you probably want to find a sub-field that interests you most before finding a project.

In grad school, we also had an ex-google software engineer volunteer with us one day a week. It was very impactful for many members of the lab to learn good engineering practices, and it wasn't at all like the sentiment others in this thread are expressing where engineers were "janitors".

https://github.com/scverse But this is mostly about transriptomics (RNA), not genomics.