PART 1:
Welcome – The introduction
https://www.youtube.com/watch?v=8paQ8mVw11M
PART 2:
Overview of the codex
https://www.youtube.com/watch?v=NHLV_OuJQRg
PART 3:
Giving back to the codex
https://www.youtube.com/watch?v=9Ab6jnuxa6I
PART 4:
Giving back to the codex
https://www.youtube.com/watch?v=ut5E02_xbOY
PART 5:
WordPress codex for theme developers
https://www.youtube.com/watch?v=u3jX5Nw2Qu0
PART 6:
WordPress codex for plugin developers
https://www.youtube.com/watch?v=n5krLICAocM