The Java RT is the minimal configuration you can have to run Java. It doesn't contain any internationalization support. This contains font mappings and a JAR file containing the international character converters, and really doesn't need to be split off by library type, but is anyway. All versions of Blackdown Java up through 1.1.7v3 required you to take the extra step of installing a package of shared libraries containing native the threads VM if you wanted to effectively run with the -native flag. Blackdown Java 1.1.8 does not require you to unpack anything special.
Internationalization is included, as well as native threads support.
For more about Blackdown Java 2, see section Information relevant to the Blackdown 2.x Java Ports . These are files that consist of a shell-script at the top and a ZIP file containing the binary archive of the Java product you wish to download. Please use binary mode. These are bzip2 compression arcvhies. However, you should have this on any contemporary distribution of Linux.