<A HREF="http://www.sun.com/chorusos/">
  ChorusOS</A>
is a proprietary _(microkernel) *(OS) rival of _(Mach), and a _(RTOS)
(now acquired by Sun Microsystems) for telecommunication
devices (cellphones, etc.) and network appliances (webphones, set
top boxes..).

<!-- dead links
See some <A HREF="ftp://ftp.chorus.fr/pub/chorus-slides/"> slides</A> about it,
and a <A HREF="http://www.cis.ohio-state.edu/hypertext/faq/bngusenet/comp/os/chorus/top.html"
  >FAQ</A>) is available here. There also are tech reports
<A HREF="http://passaic.cs.miami.edu/os/Chorus/">
  here</A>.
-->

A free, open source version of ChorusOS is now available from
<A HREF="http://www.experimentalstuff.com">
  Sun Microsystems Laboratories site</A>.