*** NOT SAYING ANYTHING ABOUT THIS SITUATION - JUST HELPING ***
IF YOU HAVE BOUGHT THIS PLUGIN:
1) LOG ON TO PAYPAL AND DISPUTE THE PAYMENT
2) SAY THE SELLER WAS SELLING STOLEN SOFTWARE
3) DO NOT DO A CREDIT CARD CHARGE BACK FOR NOW
If enough people hurry up and file disputes, you'll get your money back.
If you bypass PayPal and do a CC charge back, there's a chance YOUR account will go into negative standing (actually, I think this is pretty much a certainty) until you file a dispute against EXTREMESEO and then if you win, your account balance will go back to 0. So basically, you're going to need to dispute the payment you made to him with PayPal regardless, or it will look like YOU stole from PayPal and you'll be the one with a negative balance.
So first, do the PP dispute and wait to see the outcome. Don't do a CC charge back yet. You have time for that.