Netscape's JIT Java VM, now part
of the Mozilla project and hence open source. The commercial project
was cancelled in January 1998, and the source was released to the public in
January 1999.
The project seems to be at a standstill as CVS has not been updated
since November 1999, however it does work and will compile and run javac
without problems. It is somewhat useless for most purposes as the class libraries are very incomplete, however.
It is designed to be very portable across platforms, and is mostly
written in C++, with some platform-specific portions in assembler.