This is a bug fix release that addresses a couple of issues with thread management. In version 0.6.1, if you were creating and discarding multiple ConcurrentEvolutionEngines, the threads from the discarded engines would not be cleared up properly. This could eventually lead to OutOfMemoryErrors if you created a large number of evolution engines.
In version 0.6.2, all ConcurrentEvolutionEngines share a common thread pool so there is no need to create and destroy additional threads.
0.6.2 also reverts the switch to non-daemon threads in version 0.6.1. If you were having problems with the JVM not exiting when your program completed, this should fix it.