Reading the Linux Weekly News this week, I just found a mention of a
port of the JDK 1.1.6 for Linux from the OpenGroup in Grenoble. The URL
is http://www.gr.opengroup.org/java/jdk/linux/
The big news is it has native threads. You can't download the binaries
yet, but they said they'll make them available soon under a
non-commercial use license.
They've also got a version of gdb that debugs threads in Linux.
OpenGroup (in Cambridge) also produces TurboJ, a Java compiler that
supports Linux. Their licensing terms aren't exactly clear, but it
seems to not be free to use for anyone.