Yes the games are mini-dvds (not CDs) which means the GC is actually a DVD ROM
and as you guessed it can read CDs

Now the second issue of what this bootcd does, currently it plays GC
import games (defeating Nintendos regional lockout) and also will play
non bootable CDR copies. Currently there is NO support for DVDR copies
so you will have to RIP the GC DVD's onto a mini CDR and play it.

GC DVD2CD Ripping

STEP 1: Copy all the files from the GC DVD onto your HDD.

STEP 2: right click on the folder and see how big it is. You need
to rip it onto mulitple mini-cdrs.

STEP 3: You must seperate the game into CDs, create a folder and copy
some of the files into it (to the capicity of a mini CDR) I think they
are about 300mb so you'll be making quite a bit og folders and CDs !

STEP 4: Do this for as many times as needed, it doesn't matter what
data goes on what CD but it DOES matter that you copy EVERY file.

STEP 5: With all directories made burn each one onto a blank mini CDR.
I know it's a lot of work and uses a lot of those mini cds but it is
the way to play copies :(

STEP 6: Burn all of them onto as many mini CDRs as needed and don't
forget to burn the GC bootcd to (if you don't have it burned already).

STEP 7: Stick in the bootcd into the GC and turn it on. Options menu
will come up, select "GC Copies (multiple)" and the screen will say to
"insert CDR #1" the order doesn't matter just instert the cds and keep
following the instructions until you have loaded them all into memory
and it starts up.