_(Andy Tanenbaum)'s _(Amoeba| http://www.cs.vu.nl/pub/amoeba/), the reference among _(distributed) *(OS)es, is now free. To take full advantage of its distributed programming model, related programming language _(Orca) has been co-developed.

Even though the project was terminated in 1996, it is still developed under the unofficial <A HREF="http://fsd-amoeba.sourceforge.net">FSD-Amoeba</a> project.

The system itself is a flexible *(microkernel) with multiple servers, allowing parallel (transparent to the user) execution, resource sharing, and more.

As it was once said:
"Transparence is Amoeba's holy grail"