Where have you seen this GD-ROM emulator? The first question/answer in the FAQ (from the link you posted) says this does not turn your computer into a gdrom. Anyway, the serial link is way to slow, and was only ment for homebrew DC programming work.
About the only way you would be able to accomplish this right now is to buy a Dreamcast development "Katana" system (which is really just a windows PC with Dreamcast card, and GDRom). You will accasionally find one on ebay for around $800.