One of the advantages of any software going open-source is that in a short amount of time, you begin to see spin-off and forks, customized versions for all tastes. In less than a day after Google announced the availability of Chrome OS source, there were already builds which were floating around the internet.
What might be the use of this? Well, a version of Windows running on a virtual machine on a pendrive is abstracted from the actual hardware running on the system. This means that it is an easy matter to run your own copy of Windows on any hardware since the hardware it is running on is virtualized anyway. Although it will only run well on rather powerful machines. But then that's what ChromeOS is for!