David's code contribution to the open source community includes esky, a process checkpointing system that works under Solaris and Linux; and kernel work to better support WaveLAN 802.11 networking cards. David is also working on libkbl with Alex Smola (a C library for working with support vector machines and other kernel-based learning machines (that's mathematical kernels, not OS kernels). He also made the first British spelling version of the Linux /usr/dict/words.