That’s why the Free Software Foundation hates that term. I mean that concept is cool, they use pwyw, that is definitely an improvement.
But still you are not allowed to modify and redistribute the engine on it’s own (LICENSE.md 2.4. ), but it seems you are allowed to “to develop, maintain, extend and/or enhance CryEngine pursuant to the CryEngine Documentation;”, whatever that means.
I have no idea where you draw the line towards “Serious Games” and “simulation”, that seems very nebulous to me. Is Rigs of Rods a game or just a simulation?