If the server name is "Hobbes Test Server" then you can't get on because I am running different gamecode (Unreleased 1.0). I need to run the new code to test the changes I am making. That other player named Calvin is just me on my other PC. 8)
If the server name is "Hobbes LMS 0.35 coop Server" then you should be able to get on. I am running special code on that server but you can still connect to it.