The index.html file for the JVMTI demos is missing from Java 6 releases.
The file contains essential information for using the JVMTI demos, and is still referenced in other files in the Java 6 JVMTI demo tree. For example, the file
$JAVA_HOME/demo/jvmti/gctest/README.txt
contains the following text:
"See ${JAVA_HOME}/demo/jvmti/index.html for help running and
building agents".
The file is present in 5.0 releases, so we presume this is a simple packaging error that needs to be corrected for future Java 6 releases.