I guess I don't understand the question. Plenty of open-source projects charge money for a license. And even closed-source / non-free games have pirates. The availability of the soucre code does not determine a business model, the licensing does.

It's not really the end of the world if only some people pay for your software. You could charge for binaries but let people build from the source. You are willingly giving people the freedom to redistribute those binaries, such as to their friends. It's just not an issue. It's not a crime that needs to be prevented.