Using Nancy with Nowin (without MS.Owin or IAppBuilder).

NancyAndNowin.cs

namespace NancyAndNowin
{
    using System;
    using System.Net;
    using System.Threading.Tasks;
    using Nancy.Owin;
    using Nowin;

    public class Program
    {
        static void Main(string[] args)
        {
            var appFunc = NancyMiddleware.UseNancy()(env =>
            {
                // Optional - use LibOwin for a typed experience around env dictionary.
                env["owin.ResponseStatusCode"] = 404;
                env["owin.ResponseReasonPhrase"] = "Not found";
                return Task.FromResult(0);
            });

            using(var nowinServer = ServerBuilder.New()
                .SetOwinApp(appFunc)
                .SetEndPoint(new IPEndPoint(IPAddress.Any, 8080))
                .Build())
            {
                nowinServer.Start();
                Console.ReadLine();
            }
        }
    }
}