Quote - Is this to prevent warez distribution?

Yes.

Quote - Am I supposed to install it to my main Vue runtime, or can I install it in an external Vue runtime?

L2L items can go anywhere.

Quote - 3. Why can't I search by theme or genre?  If I click on the vehicles tab, and then on any of the other sub-tabs, I get a "0 results" page.

You have to set the "Display options" for the store.
The link is on the lefthand side of the main page, directly below the search box.