How will I be able to run commercial dreamcast games since Sega uses their own proprietary gd-rom format?
The best way is if you own a dreamcast and broadband adaptor then to stream gdrom data to icarus by running Icarus server software on the dreamcast itself. Alternatively you can dump data from your own gd-roms to an iso image and execute that from a harddisk drive. (You will need a bba/lan or serial cable to do this).