An alpha version of JNIPort 3.0 is available for both Pharo 3.0 and VisualWorks. Apart from the support for Pharo 3.0, the changes in the new release are bug fixes in the code generation for wrapper classes, the renaming of some classes both in Java and Smalltalk which had "Dolphin" in the class name, and general code cleanup. Because of the renamed classes, you will need the latest version of the archive "JNIPort_Extras.zip". For VisualWorks, it will be downloaded automatically from Store when you load the JNIPort bundle. For Pharo, you have to download it from the Download page where it is called "JNIPort30_Extras.zip".
If you want to try the Pharo version, load the ConfigurationOfJNIPort available at SmalltalkHub. If this does not work, load the packages individually in the order in which they appear in the ConfigurationOfJNIPort.
The VisualWorks version can be loaded from Cincom's Public Store Repository.