I have the same question too, not sure to be honest.
Is it possible to change the demonware id with something like cheat engine or a hex editor. Trying to create a mod for splitscreen using another program and getting bdSecurityID: already exists in lobby error when using a debugger. It works fine if you randomize your steam id for 2 players but the bdSecurityID is blocking a third from joining, saying that the ID already exists. I can retrieve my BDSecurityID but cant find it in memory in of game with cheat engine.
I have the same question too, not sure to be honest.