OpenSolaris is another alternative for us besides Linux based operating systems.
OpenSolaris is an operating system that provides a rich, coherent platform for building and running applications. The majority of the OpenSolaris code base is distributed under an OSI-approved open source license. Code based on existing open source projects continues to be available under its current license(s), and some binary-only components are covered under the OpenSolaris Binary License.
OpenSolaris supports systems that use SPARC® and x86 families of processor architectures: UltraSPARC®, SPARC64, AMD64, Pentium, and Xeon EM64T.
And, Google is also testing on it.