Do you need final cut pro to use motion 5?

You have a choice of any of the three, Motion 5, FCP X and Compressor, each one is stand alone, but interact with each other. Yes you can download only one.

My sister is using Motion 5 with Adobe Premier, she can't stand After Effects. She says its too steep a learning curve, so yes each program stands on its own.

How well does Motion 5 work with iMovie 10.0? I'd like to use Motion 5 to make a moving green screen effect like the one seen here. Any thoughts or suggestions? Thanks.

Joshua773, you can export projects from Motion as movies and import your renders into iMovie. The example you posted is actually not green screen, but motion tracking. Motion includes a built in motion tracker for things like this.

Thanks GFXZen. But can I access my iMovie library in Motion 5 via the File Browser? Thanks again

No, you will need to either export a copy of the clip in your iMovie library, or you can use the Finder. Exporting is easiest and safest. If you want to use the original media, locate your iMovie Library and right click on it. Select "Show Package Contents" from the contextual menu. Find the folder for your project, open it and then look for a folder called "Orginal Media" this is where your clips are stored. DO NOT MOVE THESE CLIPS. From here you can drag clips into Motion's Layer List or canvas and work with them. Just remember, don't change or move files inside your library.

Thanks! So if I had FCP X would my FCP X video library be available in Motion 5's File Browser? Or would I be in the same scenario as I am with iMovie?

No, you can't access the contents of FCPX or iMovie libraries directrly from Motion's file browser.