May we also use Microsoft Visual Studio licences on a customer’s IT architecture?

You may also run Microsoft Visual Studio licences for which you are the licensee on a third party’s hardware, provided Visual Studio is not used in a production environment. For a detailed explanation of what Microsoft means by a production environment, please see the following excerpt from the Visual Studio Licensing Whitepaper.

You can also find further license information on Visual Studio here.

Source: Microsoft Visual Studio Licensing Whitepaper