Recently worked through the same problem: iterate NuGet packages and get the licensing notices in a single file for a product release.

Solving it was tricky as soon as different NuGet packages provide licensing in a different way: some of them include LICENSE.txt, some use LicensingUtl tag (with broken links!), some provide README file. Mostly the task can be automated, but a small amount of packages have to be processed manually.

So, I have created a tool to use from command line or from a VisualStudio project. The tool crates a single file to include in a product release. Also it generates a log on package processing and allows to put licensing information for selected packages manually as a text file.

Source code and compiled version is available as Crossbill LicenseNoticeAggregator on Github.