I hope not; It should be an easy task for them to port this to Linux and Windows (and even to publish on the various first-party software stores they come with), given that the app is evidently built using web technologies. Perhaps even something common like node-webkit.
yup that seems to be their plan.
I saw on a post on twitter that the app is based on html css and javascript and can be ported over to other platforms and possibly be a web app. hope to see it on my gasp non-mac platform.