I make it short:
You need a valid copy of Bettlefold 3 that means >BUY IT OR GTFO<
They don´t crack it,they emulate it.That means they make their own servers and stuff like that.
Why you need to play emulatornexus if you need to buy Bettlefold 3?Well you can mod,own Server,Spectater mod and so on.(Read the Stickies for more informations!)
Will this game be free?If you bought Bettlefold 3 then yes it will be free for you then.
Is this Illegal?No,cracking is illegal but not emulating.You won´t be able to play Venice without a legal copy of Bettlefold 3.
I hope i could answer all your questions .
Revelead.