If the copyright owner is the same one releasing the iOS version they can release it in any terms they want. EDIT: it's explained in https://news.ycombinator.c

If the copyright owner is the same one releasing the iOS version they can release it in any terms they want. EDIT: it's explained in https://news.ycombinator.com/item?id=7892535 https://news.ycombinator.com/item?id=7892535 -- TL;DR: the iOS port developer has an agreement with the original developer.