Q:

Is a separate Visual Studio license required for a build machine?

I know that some companies allow you to install their products on build machines as required without requiring a separate license (DevExpress is one that comes to mind). However I was wondering if Microsoft had the same allowances on licenses.
MSBuild does not support vdproj directly and require you to run Visual Studio from the command line to build the setup project. See here
I need to produce a setup file via an automated build; do I need to purchase an additional license for the build machine?
Edit: I have spoken to our admin in charge of licensing and he was happy for me to install VS2008 on the build machine without purchasing an additional license, believing that a license should not be required. If I here more official information I will update again.
Edit 2: I have heard that Microsoft will allow VS2008 to be installed on a build machine as long as the instance is not being used by a developer for active development.

A:

Here is the agreement (PDF link!).  (There are different ones for different versions of VS).  So it depends on how you read ...
General. One user may install and use copies of the software to design, develop, test and demonstrate your programs. Testing does not include staging on a server in a production environment, such as loading content prior
to production use.
To me that says you don't need an additional license because one user can install and use copies.  But, I am not a lawyer. :)

A:

According to the VS 2015 Licensing White Paper, you do not need a separate VS license for your build server:

Using Visual Studio on the Build Server: If you have one or more
  licensed users of Visual Studio Enterprise with MSDN, Visual Studio
  Professional with MSDN, or any Visual Studio cloud subscription then
  you may also install the Visual Studio software as part of Team
  Foundation Server 2017 Build Services. This way, you do not need to
  purchase a Visual Studio license to cover the running of Visual Studio
  on the build server for each person whose actions initiate a build.

Update (May 26, 2017)
Microsoft has also now published the Visual Studio 2017 Licensing Whitepaper as well, which has the exact same requirements as noted above.

