http://www.gentoo.org/doc/en/java.xml
3. Installing a Virtual Machine

The default is Blackdown for both the JRE and the JDK, as it is freely ("free as in beer") available without any registration fuss.

The default for Java 1.4 is the Blackdown JRE/JDK pair, as it is freely ("free as in beer") available without any registration fuss.