OK well first off they list that it also works for GameCube discs, which is odd because
no drive can read them in the first place.
Second...
it is not physically possible. 4.8GB will
NOT fit into 700MB reliably. Some games do in fact fit, because they don't use all the space available... but many games are starting to use filler at the very least to exceed 700MB (Mortal Kombat: Dark Alliance comes to mind

)
If you want to try it, more power to you, I'd love to see this debunked.
Addendum: Hah, such BULLSHIT!
"Wow - XBox and Gamecube Backup copies in less than 15 minutes, never thought is was possible with just my PC! Thanks..KJ"
Says one testimonial. Gamecube backups? So why are there no rips available? HMM... I WONDER...
False testimonials have been done before...
Second addendum: Even better.
One of the popups on closing the site said:
Copy any DVD, Xbox, Playstation 2 & 3 !!, Gamecube Game in 30 SECONDS w/your PC!