There are VDA per User Add-on SLs added to the February 2017 Product Terms document. These are designed to be added on to VDA Device SLs and follow the same rules as the Windows 10 Enterprise E3 and E5 Add-ons. See pages 38 and 42-43 of this document.
The February 2017 Online Services Terms document adds some clarity around Dynamics 365 licensing. Firstly, external users don’t need an SL if they’re using the Operations service, but if they’re using Dynamics 365 clients to access the other services then they do. And secondly, it’s confirmed that if you’re licensed for Dynamics 365 Business edition then you don’t have the right to install and use Dynamics 365 on-premises server software. See page 3.