This is a preview for journalists and developers, since for the final release or any RC (release candidate) the wait is long. Currently there is no demo available, but Google has announced that the source code will be "completely open", just to invite curiosity and independent programmers to work in advance about new improvements and add-ons to the basic core of the software.
Chromium OS is an open-source project that aims to build an operating system that provides a fast, simple, and more secure computing experience for people who spend most of their time on the web. Here you can review the project’s design docs, obtain the source code, and contribute. To learn more about the project goals, read the announcement blog post.