Usually it is not required to use your own API key while publishing your code. Make sure you have explained it in documents how other developers can acquire their own APIs. And that should do it. But if you want to include it anyway you can give this article a read - https://code.tutsplus.com/tutorials/protecting-your-keys-from-github--cms-23002

Ya, this comes down to how you want to publish your project. I'll add that since we don't charge for the API, it's not usually a big deal to get people to register their own but if you make the choice to include yours, the main issue you might run into is that someone could take it an abuse it. In that case we block it and you would need to get a new one, but everyone who is using your project would also need to do that (whether it's an update you publish or otherwise).

Your call on the matter but that kind of explains both ways to think about it.