I'm not so sure. If you're the sole developer, you can offer the binary on iOS and UWP with a standard license, while having the code on GitHub under e.g. BSD l

I'm not so sure. If you're the sole developer, you can offer the binary on iOS and UWP with a standard license, while having the code on GitHub under e.g. BSD license with a note "Game contains code from GameCore licensed under the BSD license". Basically you license the source code under BSD to yourself and you create a derivative that includes all assets that you retain all rights to.