No one seems to understand..
No, he did not code up Doom from scratch. He took the original game and (using the technology of Adobe Alchemy) he allowed the game to be run in Flash inside your browser. (For heaven's sakes, read up on Adobe Alchemy if you don't understand...)
While I don't doubt that a lot of effort was still necessary to make the game more playable in a browser window, it's insulting to praise a programmer for the things he did not do.
Still, great job putting up Doom on the web. This has surely brought good memories back to a lot of people out there.