To check out code, use a command such as:
darcs get --partial http://darcs.realworldhaskell.org/rwh
For more information on Darcs, please consult the homepage, wiki, or manual.
For more information on the book Real-World Haskell, please consult its homepage.
If you are interested in the draft of the book, rather than its source, you can view it in online HTML or PDF form.