One part of my full time job these past fifteen plus years has been to help maintain a foundational open source library that my employer and many many others are dependent on.

When it comes to total impact of open source work, I’m unlikely to ever surpass that.

I’m still using good ol’ Xournal. It isn’t really particularly good (and I’d be happy to find something better), but I’ve been using it since forever and the force of habit is strong.

https://en.wikipedia.org/wiki/Xournal