I have one library using one function in the PnP configuration manager library. Therefor, the cfgmgr32.lib is included in our build.
But I don't know where it came from, nor do I know what license is attached to it. I assume it was in the DDK.
Could one label this as "Proprietary" software?
First I assume that you are talking about a lib that is part of the windows driver kit: http://msdn.microsoft.com/en-us/windows/hardware/gg487428
Per: http://msdn.microsoft.com/en-us/windows/hardware/gg487463 "How to get the Windows DDK"
I end up there http://www.microsoft.com/downloads/en/details.aspx?displaylang=en&FamilyID=36a2630f-5d56-43b5-b996-7633f2ec14ff and a download url of: http://download.microsoft.com/download/4/A/2/4A25C7D5-EFBE-4182-B6A9-AE6850409A78/GRMWDK_EN_7600_1.ISO ...
This is a large ISO image. Once you have that, the terms of the license should be detailed in the ISO somewhere.
Per: http://www.microsoft.com/taiwan/whdc/devtools/wdk/RelNotesW7.mspx#EPD
"The contents included in the Windows Driver Kit (WDK) are licensed to you, the end user. Your use of the WDK is subject to the terms of an End User License Agreement (EULA) that accompanies the WDK and is located in the WDK installation directory. The name of the file is License.rtf. Before you access or use the WDK, you must read and accept the terms of the EULA. If you do not agree to the terms of the EULA, you are not authorized to use the WDK."
So get the ISO, install and get the exact license.
Also the doc is there: http://msdn.microsoft.com/en-us/windows/hardware/gg487458
this is smaller and should also contain license terms.