If one wanted to make a game and license the very newest and hottest engine out there - say something like the new Doom engine - it would probably set you back about a quarter million dollars. So, by my calculations, licensing the Myth II engine would cost, oh, approximately $3.98 and two box tops to Grand Theft Auto. Well, not really, but you get my point. Consider also that this is an engine that its current developers already have a good handle on.
Licensing the Myth franchise/name along with the engine is a whole other proposition, and I'm somewhat doubtful that can even be done. Buying it would probably be the only option, and I'm sure that would be quite expensive, not to mention a big hassle considering its rather split-up state at the moment.
You're welcome to discuss proposals with Project Magma, Dark Sword, but really, I would suggest you first think long and hard about what sort of return on investment you're looking to make. And forget the money part - like a new romance, the "hey, I've got a windfall and an idea" stage is a lot of fun; everything afterwards requires true dedication and endless compromises.