"Free commercial use" allows the standard sort of use allowed by most standard commercial font licenses. Web graphics, posters, t-shirts, signs, logos etc.
If you're going to embed the font in an app or a web page, there's a different licence for that. I recommend Fontspring.com for those.
However, if the font isn't "embedded" in the app, you can still use it with the regular, free license. For example: titles screens, headings, labels, the app's icon . . . situations where it's just a graphic and not the actual font embedded.