After reading your post I tried unzipping the nuget package and I was able to see the DLL’s that are in the custom package, So DLL contains machine code/byte code as .NET run-time supports more than 60 languages , I don’t think we can convert them to the original language in which the code was return how ever third party tools are available to decrypt the code to c# and VB but I dont know how reliable will be the code, and You have to obey the Nuget pacakage license before you do any thing with the code or DLL. I think they are distributed as to use. unless specified like open source license.