While I'm only an amateur programmer with the most rudimentary skills, and in no way an authority on the subject -- there are several approaches I'm aware of. I think the most significant point though is Open Source is OPEN, and creates a lot of good will that you don't see on commercial software products that keep things from getting broken in the first place, and get you more help when you need it most.
I'm sure many talented would be game hackers would as their counterparts have in Linux turn to more productive and satisfying security and countermeasures development.
But I suppose you want a more focused answer; two approaches I'm aware of are registered encrypted key served binaries, and the security module does not HAVE to be Open Source; it can be a separate closed source project.
The bottom line it's not possible to eliminate hacking by any means, but Security Through Obscurity doesn't work any better, and breaks means for a wider more capable audience to address the issues of hacking, exploiting, and security.
.