Below I list a number of projects or hobbies that I am either actively working on, or have worked on in the past. Some of these are related to my research, and some are not. I leave the problem of deciding which is which as an exercise for the reader.
Kidney exchange programmes improve access to living donor kidney transplants through effective allocation of resources. I am the developer of kep_solver, a package of kidney exchange software that allows for the modelling and optimisation of instances of kidney exchange programme problems according to various criteria and with various other constraints. The source code is available under the GNU GPLv3 open source license.
I have also developed a game - The Kidney Exchange Game that explains some of the basics of these programmes.
Gentoo is a Linux distribution that I have used for many years. I don't necessarily recommend it for everyone, I think of it more as aimed at those who like tinkering. Within Gentoo, I support a number of packages, and provide occasional support on IRC. The packages I help maintain are: