Thanks for raising this question around restriction access to people search and the homepage. I've looked into this and don't see that this is feasible out of the box. It may be possible to explore this via theming and customization, but as this will require development work, the subject is outside the scope of Jive Customer Support. If you're working on developing this yourself, I would recommend posting a question to the Developer space, or you or I could move this thread there. Otherwise, I would encourage a Jive Professional Services engagement.
Let me know if you had any other questions.