These are alternatives that be DnD like and in some cases can use DnD or replace it. Look them through to fulfill your curiousity! Even, feel free to play the game as described. There's Free download of them in the Alternative DnD Roleplay 5 archive. Updated 7/22/2017.
Arda magic system v3.3; Modified 7/2/2017
Ars magic DnD 3.2; Modified 7/22/2017
Live Ars DnD 3.3; Modified 7/23/2017.
Live DnD 1.1; Modified 7/23/2017.
Nabbles RTD; Modified 6/27/2011
Nabbles RTD Advanced; Modified 3/27/2017
Newport erth rolls to see; Modified 6/27/2011
These are games that are based on DnD and other RPGs and is what life could be like, if DnD and MMORPG were real.