Upgrading to El Capitan is a good idea, but it won’t solve this problem.
As of the latest RhinoWIP, this is intended behavior. If you have an expired evaluation license, Rhinoceros and the RhinoWIP should switch into “Expired Evaluation Mode” - which essentially turns Rhino into a viewer. You cannot save, export files, load third-party plugins, nor run ExplicitHistory or RunPythonScript.