> That way your project is just a mod.
Little correction needed. "Mod" usually mean derivative work of original game, but open source engine projects are not derivative work.
So it's just an engine that have nothing to do with original game or it's copyright holder.
Re:Show HN: HTML5 version of StarCraft
by ponytech on Monday September 07, 2015 @07:39AM
(#10181035)
See also https://www.openttd.org a remake of Transport Tycoon Deluxe.
Which over the years and thanks to a massive effort of contributors have managed to create its own set of graphical and sound assets and is now a stand-alone game.
(Still some copyright issues remain)
Here's something interesting, an open source Warcraft II style engine https://en.wikipedia.org/wiki/Stratagus
You'll have to adapt the same strategy as they do, or any other engine remake: Host and share your engine, require the user to themselves supply the original game installation. That way your project is just a mod.
Another example of a great engine remake is "RttR" http://www.siedler25.org/ a remake of the Settlers II engine. They require a separate installation of the original game to play.