One of the things about Java is that the older APIs encouraged/forced the use of many threads. MS Windows, in particular, bogs down when there are tons of threads.

Java didn't even have non-blocking TCP sockets until Java 1.4. Now that most Macintosh users have a Java 1.4 JVM, LimeWire can start using the more efficient 1.4 APIs without leaving anyone stranded.

The new LimeWire beta version uses one thread to handle all of the TCP connections, rather than needing two threads for each and every TCP connection.

You might want to try the new LimeWire beta version. It's much more efficient with large numbers of connections.