I contribute to a number of open source software projects on a regular basis. An overview can be found on OpenHub.
FreeBSD is an open source Unix-like operating system that can be found (as a whole or in parts) in Apple Mac OS X and iOS, Sony Playstation 4, Juniper routers and NetApp storage filers, to name a few. I have been a developer with the project since 2003, and also contribute to related projects like TrustedBSD.
BSD Magazine 04/2009 – FreeBSD Security Event Auditing