Well, I have seen too many cases of this happening... mostly by original authors. In some cases (Fairlight remake by a friend of mine) they wanted the source code to be given to them for free so they can sell the game on all platforms they want. Ofcourse the author has told them where they can stick it... ;-)
There are numerous cases like this (CodeMasters, Ultimate Play The Game, etc.) and all of them say they want to protect the copyright... well, I just don't buy that. It never harms them if someone makes a FREE game... it is just a good advertisement if you ask me. They will never be able to sell it for Win32, DC, MacOSX, etc. Maybe for GameBoy Advance, but I dont think that version was on the site (but I never saw it, so I have no idea).
But as you said - it is the authors copyright and if he wants to do that he can.. I just don't think it is a nice thing to do - someone had gone to a great length to code a FREE engine for a game that is a decade or more old basically as a tribute to them.