みんなネタだとは思うけど、勘違いする人がいるといけないから。
以下はsunのページにあるQAから。

1. Is JavaTM technology free?
Most of the java.sun.com products and API's are free to download
and to use for commercial programming, including:

J2SE SDK (previously named the JDK)
JRE (latest version)
J2EE SDK
J2ME related technologies

The J2SE SDK and the JRE can also be freely redistributed,
provided that it is distributed with a value-add application
or applet. Each release has its own license, available from
the product download page.

Please note that prerelease software
(For example the JRE v1.4 Beta) is not free to redistribute.
We encourage developers to use production versions of the software.