Does anyone know where I can get the specs or source for the
   NFS lock protocol (you know, what lockd ordinarily implements).

I'm not sure about V2, but you can get the NFS V3 spec from:

playground.sun.com:/pub/nfs/NFS3.spec.ps.Z

Rick Macklem was working on implementing NFS V3 functionality (mainly
64-bit offsets) in the BSD NFS implementation.  As far as I know, he
hasn't done any work on lockd, or have any plans to.

(Note to everyone else: I assume he will resume his work on V3 soon,
so I wouldn't suggest that anyone else bother at this time.)