So your original post is about a hypothetical situation, is it?
On itch this question does not arise and I am wondering how you even got the impression it was possible, as you might have noticed.
The platform hosts the files and deals with access to your project after a purchase. That is what leafo was referring to. You would have to implement drm on top of the restriction that only a paying customer can access your paid content.
And your first language does not change by moving ;-) Native language is another word for it. It is a statement about the past. Not a statement about which langauge you know best or speak daily.