Yes it is against God’s word and your soul is the most priceless possession you have and if you could sell your soul that way then I would say don’t do it. However, this site is so obviously satire.
Besides, the soul cannot simply be harvested from your physical genetics, and the devil likely doesn’t have the power to go around sucking the human soul out like that. If the Bible doesn’t mention it then that’s that, so before you go falling for this perhaps you should check God’s word to see if it mentions any fancy soul-sucking devices first. And if your soul gets sucked out of your human body then it’s all over you don’t live on just being your human body.
So sorry folks but if you want to sell your soul you’ll have to do it the old fashioned way. Follow a path of sin, refuse God’s gift of salvation, not repent and keep on following your own sinful desires till it leads to your own destruction. And though I REALLY advise that you not follow through with that I really think that people shouldn’t take this stupid site so seriously.