FreePastry is described as 'open-source implementation of Pastry intended for deployment in the Internet' and is an app in the File Sharing category. There are three alternatives to FreePastry for a variety of platforms, including Linux, Mac, SourceForge, Windows and Java. The best alternative is Chordless, which is both free and Open Source. Other great apps like FreePastry are Open Chord (Free, Open Source) and NChord (Free, Open Source).
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.
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.