[...] if you modify the Program, your modified version must prominently offer all users interacting with it remotely through a computer network (if your version supports such interaction) an opportunity to receive the Corresponding Source of your version by providing access to the Corresponding Source [...]
I'm not a lawyer so I'm not sure if that means he should link the source code on the website itself. He technically does offer to access the Corresponding Source by posting a Mega link here.
I'll keep my distance on this regarding the license, I still believe this was an honest mistake.
The modified version must prominently offer its source code to all users interacting with it. Not all users reading a particular thread on a particular forum.
I'm willing to believe he didn't understand the license he was agreeing to. But now that it has been brought to his attention, that's not really an excuse for continuing to fail to comply with it.