Open Chord is described as 'OpenChord is an open source implementation of the Chord distributed hash table as described in the paper by Ion Stoica et al'. There are three alternatives to Open Chord for a variety of platforms, including Linux, Mac, Windows, SourceForge and Java. The best alternative is FreePastry, which is both free and Open Source. Other great apps like Open Chord are NChord (Free, Open Source) and Chordless (Free, Open Source).
NChord is a C# implementation of the Chord distributed hash table. The project provides a library containing the routing, lookup, and maintenance routines specified in the MIT Chord paper, and is quite stable including under heavy load and churn.
Chordless is a Chord and DHash implementation written in java. It implements almost everything from Chord and DHash described at http://pdos.csail.mit.edu/chord/ , as well as some extra features such as transactions and remote method invocation.