So what he did was puting a already made gpu miner code in your wallet code, and compiled it?
Already made GPU miner? There was no GPU miner, he is the first who made it.
But he would have just edited one the was already made and put it into the wallet, right?
I think he used existing code for X11 part but SpreadCoin algorithm is quite different, its not an easy task like just copy & paste some code. Even X11 part is different because preexisting X11 miners are designed to work only with specific block header size which is different in SpreadCoin.
He didn't actually put it into the wallet. It is an external miner, he probably modified the wallet to work with his miner.