Have a look at the GitHub repo
there was a recent check-in (a few hours ago of this comment being posted) https://github.com/spring-projects/spring-net/commits/master
also gives you an idea to who is developing the library.
forum looks to be up and running.
however that said, the same question is being asked on the forum http://forum.springframework.net/showthread.php?10866-Current-state-of-the-Spring-NET-project