Making it closed source is dumb. It's not like any features you add will change the fact that vb6 is a laggy piece of garbage that you can't actually make an "MMO" with, let alone a small online game that can barely serve 20 people. There's already better engines out there for game creation that are open source.
Not that I'm really interested in the engine. But, at least make it open source so if someone needs a few extra features to make their game unique they can. You've got nothing to lose. Anyone who can actually benefit from your code (a programmer worth their weight), will already know how to implement the features anyway.