Reverse engineering and pirating are not the same thing (although the former may certainly be used as a means to achieve the latter). As long as you aren't distributing the game, distributing code that legitimate owners of the game can use to run their game on more platforms is not a crime.
>distributing code
The code is also copyrighted and owning a license for a game does not make you safe from being sued for pirating that game or its code. It's fine in this case only because the engine was open sourced.
In systems engineering this was proven in court when you have one engineer writing specs and another implementing the "samish" system from those specs, but I'm not sure that would relate to any of the art assets made by the original authors of a game. I'd imagine any art, narrative writing or sound would still be considered IP, and without those things you don't have much of a game.
I suspect it won't stop people, and that it won't be much of an issue in a lot of cases. I wouldn't want to be the one to test it in any sort of court though. Not even on the other side of things, where it'll become even more of a nightmare to protect your indie IP on any form of platform which doesn't heavily regulate things.