Is there ANY legal and free way to run a Mac OS(virtual or not) on a machine I did not purchase from Apple? What about purchasing the parts separately and assembling them myself? Does that make it any more legal?

The short answer, is No. The issue is that Apple’s End User License Agreement, prevents this.  You know, the EULA which you didn’t read, and just clicked past it.  That little piece of virtual paper prevents you from doing this.

2. Permitted License Uses and Restrictions.

A. Single Use License. Subject to the terms and conditions of this License, unless you have purchased a Family Pack or Upgrade license for the Apple Software, you are granted a limited non-exclusive license to install, use and run one (1) copy of the Apple Software on a single Apple-branded computer at a time. You agree not to install, use or run the Apple Software on any non-Apple-branded computer, or to enable others to do so. This License does not allow the Apple Software to exist on more than one computer at a time, and you may not make the Apple Software available over a network where it could be used by multiple computers at the same time.

Now, that was the short answer.  The technical answer is that since the EULA is what prevents this, then what if we could find a  country where the EULA has no legal value.  Well, I don’t think you are going to find this Fantasy Land, and if you do beware, the Crime rate will be quite high.  To some extent, all countries enforce EULA’s, some have different restrictions in place, but all of them enforce this rules to some extent.

But this doesn’t mean that your completely out of luck, remember an operating system consists of many parts and large parts of OS X are indeed free. If you are interested in this have a look at the Darwin project. What is missing from Darwin is mainly the graphical user interface of OS X (Aqua). You can run GNOME or KDE instead if you like. One of the consequences is that you can’t run applications that depend on Aqua, like Safari or iTunes.

Now virtualization is a 50-50 split.  From Snow Leopard’s EULA:

Subject to the terms and conditions of this License, unless you have purchased a Family Pack or Upgrade license for the Apple Software, you are granted a limited non-exclusive license to install, use and run one (1) copy of the Apple Software on a single Apple-branded computer at a time. You agree not to install, use or run the Apple Software on any non-Apple-branded computer, or to enable others to do so.

You can, however, legally virtualise Mac OS X server, but only on Apple hardware.

This License allows you to install and use one copy of the Mac OS X Server software (the “Mac OS X Server Software”) on a single Apple-labeled computer. You may also install and use other copies of Mac OS X Server Software on the same Apple-labeled computer, provided that you acquire an individual and valid license from Apple for each of these other copies of Mac OS X Server Software.

So server’s can be virtualized, but not the consumer OS.