This is a minor release. It fixes the issue of not able to run the game with a JVM 1.5, which seems to be the default config for Mac OS. It improves the animations under OpenJDK. You don't need to upgrade to this release if you don't want to play the game with a JVM 1.5 and if you don't use OpenJDK.
This release fixes a severe AI bug that could greatly weaken it. Thus much work has been done on memory optimization to make the AI player much faster. Two new AI levels have been added thanks to the optimizations, which make the AI player much harder to beat.
This version fixes many bugs of the 1.3.3 release. Thus it brings a huge speed improvement when using the AI game player and some various small goodies.