I work extensively on open source software.

• FreeBSD, the premiere open source operating system, at the heart of many of the systems that run the Internet.
• PTPd, the Precision Time Protocol Daemon, a BSD licensed implementation of the IEEE-1588 protocols, used to closely synchronize LAN connected hosts.
• PCS, the Packet Construction Set, an easily extensible Python library used to write network testing and validation tools. 
• Packet Debugger, a tool, based on PCS, for interactively working with packet streams such as those collected with tcpdump. 
• Conductor is a system for controlling distributed systems during tests.  It is meant to replace testing by hand with multiple ssh sessions or depending on a ton of random shell scripts to execute network based tests with multiple clients.