Disclarimer: I am not a lawyer. Software is tricky.
Technically the written work, (the source code), is original work even
though it accomplished the same thing, so he couldn't be sued for
that. I don't know if the artwork is the same, I never played the
original game. In terms of artwork and music, if those are similar
then you could be sued for that. I don't know if anyone has a patent on
the game play, but that's something to consider. Apple and
Microsoft have patents on their GUI and the functionality of their GUI,
and someone could probably start patenting those concepts in
games. Of course, patents, copyrights, and trade marks are all
different concepts in terms of the law, but you can still be sued for
infringing on any of them.
The only protection that I know of is to create a parody of the
game. However, I don't think this work as it is could be
classified as a parody. If you were to change the graphics to
something else, such as pictures of the U.S. President, then you could
probably argue that version of the game as a parody. Their could
still be one remaining problem. A company could still file a
lawsuit against you to bring you to court even though they may not win,
it will cost you lots of money for legal fees. This tactic is
used to bankrupt people into doing what the larger company wants them
Of course, there really is no money in this sort of game. I can't imagine Lolo 2 outselling Halo 2.