Even IF it's true, and even IF it works on machines other than the dev kit Apple are providing, I find it hard to believe it will work on the vast variety of PC hardware out there, especially graphics and sound cards, think of all the drivers required! I've had headaches of the last few years getting not only Linux but Solaris to work on standard PC kit. Regardless, I wouldn't read anymore into this than the pics of the internals of the dev kit, it gives absolutely no indications of final products, the dev kit probably is a fairly generic mobo and the OSX/x86 as it exists now probably works on a few combinations of hardware but it means nothing.
If true, installing it on a PC is really risky, if Apple did find out, there could be.. problems. I also expect the OS will be date-limited too. It won't be difficult for Apple to tie the OS to the dev kit it was intended for (if they are clever), that developer better be ready for a visit from Apple's lawyers.