Legally there's no such thing as abandonware.  So, even if there wasn't a live entity that owns the IP (there is), anyone developing a game for profit without the copyright holder's okay would certainly be in the courts and would lose (given that there's a live entity holding the IP, that'd likely be the case even if the game was not for profit).

So anyone developing a game is faced with the option of acquiring the rights or designing something similar.  It might be worth acquiring the Dune rights for a Crusader-Kings-II-in-space game, but I'd assume the small market for that sort of game means that there's not a lot of profit to be spread around on acquiring rights.  For something as relatively unheard of as EFS, companies such as Stardock would just make their own universe up.

Love the universe though, even if the SP game was just too unfinished to be enjoyable after a couple of plays.

HonestlU y, Stardock has programmers. The courts r going to sue them on coding not how the game is played. For the most part reverse engineering is legal. There r probably rules to this. There is a certain amount of code that would have to be changed to make this legal/ if stardock accidently came up with the exact same code then u r right, but what is the chance of this happening considering that things change. Not to mention stardock is not going to trade for a older game enginge. The engine should be enough of game difference to make this to work. U also have to remember that they r only adding to the game not using the other game. He did suggest Stardock knows how to do this. All I can say is that I never played this game, so I can't comment on how good of an idea this would be. U also have to remember that is there anybody who would sue. The company may of went out of business.

Holistic Design Inc is, AFAIK, still active.  Not that that matters; there's always going to be someone who owns the rights.

We're not talking about the code, which was worthless within a year or so of release (given how unfinished it was, probably sooner ), we're talking about the IP to the Fading Suns universe.  Same with Star Wars, Star Trek, B5, etc.