you can work around that issue if you make an empty asp.net project and then use nuget to install-package nancy.hosting.aspnet
at least i think so, i haven't been doing .net in a while
http://rubygems.org/gems/albacore/versions/1.0.0.rc.1 (for the command to install albacore), and
https://github.com/NancyFx/Nancy/wiki/Running-Nancy-on-your-...
This works on Fedora and probably other distributions as well, though this uses HTTP which might be less optimal than FastCGI with Fos. I got Fos to compile with Mono but it's not usable yet, it can't find IAppBuilder in my "console" application no matter what references or using directives I add. Nowin compiles cleanly but the example projects don't, so it'll take some effort to get it to work. Things are progressing, though. But I really can't recommend anyone use Mono for web development as it stands.