Office Web Apps Server 2013 without SharePoint

I noticed that Microsoft has released a new version of Office Web Apps Server 2013, which is now a standalone product.

I'm looking for a mechanism that I can convert Word / Excel and PowerPoint documents to a web version (HTML5) for an application that I created that uploads these documents to S3, and I thought Office Web Apps Server 2013 Standalone would work.

I don’t want to use Google Docs, but rather use the solution that I have.

Reading Office Web Apps Server documentation does not indicate whether I need to have a SharePoint server license. I tried to deploy Office Web Apps Server on a Windows 2012 server on Microsoft Azure, and although the software is installed, it cannot display any documents that I point to from an external URL (S3 public bucket).

Does anyone know which specific requirements of Office Web Apps Server 2013 are working correctly? The website states that it can be used to view documents from the external URL that I am trying to use. But since this is a new product, there is not much information on it that I could find, other than instructions for deploying Microsoft.