The FAQ link now just points to the product download page, but near the bottom, under Additional Information
> Commercial use of Visual Studio Express
for Visual Studio Express 2013, it states:
Visual Studio Express products are available at no charge and may be
used for commercial, production usage subject to the license terms
provided with each product. For example, you can use Express for
Windows to create apps that you can then submit for sale in the
Windows Store.
As of 3/21/2014 there are 5 products each available for commercial usage, but in different areas:
- Express 2013 for Web
- Express 2013 for Windows
- Express 2013 for Windows Desktop
- Team Foundation Server 2013 Express
- Express 2012 for Windows Phone
You'll want to consult the EULA of the version most applicable to better understand the restrictions. But I believe those restrictions will be evident in the features of the software. Meaning I don't think you have to worry about the Windows Desktop version allowing you to write Phone apps that are allowed in the Windows Phone version, it just won't allow you to write them.