It is not correct to say that GWT is meant to develop applications that run on browsers. As we know GWT is based on Java and translate Java to JavaScript, and also includes IDE and Ui support which helps to make web apps. You can make some application wrappers that takes JavaScript applications native to androids or other operating systems of mobiles. This is how you can design mobile apps with the use of a glue layer present in between native wrapper and GWT for a JavaScript app.
Yeah, it is true that you can't make apps only with GWT, instead, you need other libraries. Thus, it is fully possible to make apps using GWT by combining it with other libraries
