Is there any free *nix guest/guest terminal login without a need to register in order to use it ?
Ask Google and ye shall receive: "The biggest Free Shell list on the net :-)"
sdf in Dallas used to be a 4 line dial-in publicly accessible Unix system. It's been many years, but don't give up. Use google and be diligent and flexible in your keywords. You're probably asking in the wrong forum.
believe it or not, SDF still exists with the same philosophy and goals.