OpenSolaris

"Today, Sun announced that the source code for the Solaris
operating system --the most advanced operating system in
the industry--will be made available through its OpenSolaris
program. This milestone opens significant new opportunities
for students, faculty and education software developers.
Open source Solaris means that the world will have full,
free of cost access to the Solaris source code. Sun
believes that the open source model is the right one because
it benefits our customers. Open source means that our partners
and customers will be able to more easily customize Solaris to
fit their needs. It means developers ouside of Sun will be able
to collaborate with our Solaris developers at Sun to make this
great operating system even better.

OpenSolaris