Essentially this sits in the request pipeline, intercepting HTTP calls and providing hooks to do authentication outside of IIS. This allows for implementing basic / digest auth easily without involving IIS and it's dependency on being tied to Active Directory, rather than to a database, which is the usual implementation.
At one point this was a viable security infrastructure that was intended to be cleaned up and open-sourced.
The code should still work fine, and work well -- but it will require a bit of polish to ensure it's well tested and can be officially released on NuGet.
If you're still working in a Microsoft world, and haven't moved on to something like ServiceStack and it's simple plugin architecture, then this might be a good fit for you.
There are a handful of nifty tricks around mocking, and providing
lightweight handlers for Authentication, based strictly on Func<>.
At one point this code used a Git submodule for build tooling -- that has been removed, but the projects haven't been properly reconstructed or setup with a tool like Psake -- that work would need to be performed before this can even build.