It is not platform dependent. You can use on Windows, Mac, WebTV, etc. In short, DOM is a standard that actually does only what it is supposed to do. IDL or Interface Definition Language. All languages can then use it.
All platforms can then use it.
But, why should the designer of the Holodeck be tied to COM or Java technologies. But that does not mean standards should hold back innovation in new technologies. One of the main reasons was device support was limited. Device Vendors don't like to write device drivers for multiple versions of windows, let alone for other operating systems. Implemented under Windows 98 as a VxD, it allows a common device driver to be used Win98 and WinNT5.