I quote from the Sun JXTA pages which have a December 2002 date,
"Project JXTA has a Java reference implementation available from download.jxta.org, and is currently working to add reference implementations in other common languages, including C, Objective C, Perl, Ruby, and Python. Though the Java implementation is the most complete implementation of the JXTA protocols, the C implementation (available for both Win32 and Linux) is fast approaching the same level of completeness."