As a concrete example for the copyleft distinction, consider if Swift Foundation was founded to create copyleft (let's say GPL or even AGPL) compilers, but the system libraries every compiled program would need to link to were only found on Apple products. It's very clear that this would be a move that would be for the benefit of Apple's bottom line, and that it was a technology originally developed by Apple employees. So it's not like some random guy in his garage said "I will make something charitable but make the independent decision to base it on Apple hardware," as is true of (say) an iPhone app for detecting medical problems, which would indeed be 501(c)(3) eligible in my book (IANAL).