Demakes are a regular thing in the independent homebrew community. Some commercial companies have even given their blessings as long as the games are free, non-profit, endeavors. Konami seems to be a case by case basis, Sony too, Microsoft has pretty much okayed a demake of Halo for Atari 2600 in the past (nothing else that I can think of right now though) and well, Nintendo is Nintendo - they have lawyers just waiting for someone to make anything similar to their IPs.