Here are links to the slides from some darcs-related talks given by David Roundy:
CS Colloquiem Talk from OSU, 20 November 2006. "Verifying the darcs patch code."
FOSDEM talk from February 2006. "Implementing the darcs patch formalism ... and verifying it"
- This talk covers the patch formalism and the use of GADT type witnesses to enforce patch relationships.
There's also a video (270M) of the talk (albeit a bit blurry) available.
- This talk covers the patch formalism and the use of GADT type witnesses to enforce patch relationships.
Haskell Workshop talk from 2005. "Darcs: Distributed Version Management in Haskell"
- Talks about experiences of darcs with the Haskell language.
CUFP talk from 2005. "The Myth and Reality of using Haskell in the 'Real World'".
- Addresses experiences with finding contributors for darcs, given that it's written in the Haskell language.
(Note: Anyone who cares to would be welcome to write better summaries...)