You can find an extensive bio him on his company's staff page. His work resonates especially well with DIYDSP because of his concise goal statement:
"how to play live interactive music in an ensemble using extended instruments moderated by computer intelligence"
DIYDSP has the same goals, except that we are focused on creating the entire music instrument. The work on Keith's website focuses on instrument controllers. Perhaps soon, some collaborations will be possible. Keith's interfaces are based on standard protocols like USB and MIDI interfaces, so the compatibility is possible.
"If anyone walks the line between Steve Jobs and Bob Moog, it's Keith McMillen." - H. Haynes"