The email address and password the planner asks for is only there so that you can save itineraries as you are planning them. It is not related in any way to any airline or program. You only need an account if you have or want to save itineraries.

You can access the planner without having an account or saved itineraries on oneworld.com. Just click on the "Plan and Book a Round-the-World Itinerary" or "Plan a Multi-city itinerary" links and use the tool. If you then want to save your planning, it will ask you to log in or create an account.