The only way to protect code running or content playing on an open system is security by obscurity. As a developer, choose your trade-off on the scale between inconvenient-but-quite-secure and simple-but-easy-to-copy and go with it. Any protection will be broken in time. Adjust based on customer feedback and the amount of cracking going on, but that's pretty much all you can do from a technical perspective.

NB: at a low enough level, all systems in the hands of the attacker are open. Hardware DRM is vulnerable to attack by equipment for scraping layers of atoms from the silicon and inspecting it with an electron microscope.