Apple - Is there a way to use Live Photos in iMovie?

Yes. You don't have to buy any software. Here's the procedure for transferring a "Live" photo taken on an iPhone 6 on to a Mac and then into iMovie or Photos as a movie file:

1. Connect your iPhone to your Mac using a USB cable
2. Open "Photos" on the Mac.
3. Select your phone icon should be under a grey "Import" title in the sidebar.
4. Select the "Live" photo(s) and import them.
5. In "Photos" select the "Live" photo you want to convert to a movie.
6. In "Photos" in the "File" menu select "Export"=>"Export unmodified original..."
7. Select a location to save your movie (container) file. It exports the file as a .mov file.
8. You can open and play this file in Quicktime. But...you're not done yet.
9. Right click on the .mov file. At the bottom of the menu select "Encode selected video files". IT takes a few seconds.
10. Now you can choose 480p, 720p or 1080p.
11. Save your file (it is .m4v format)
12. Now you can import this file back into "Photos" and share it as a movie or you can drag it to iMovie and select frames, edit etc..

My workaround is to use the Google Motion Stills app to create a video from the live photos and then insert this video in iMovie.

All done on an iPhone.

If you are wondering if there is a way to extract the video from a Live Photo, there is. But not directly through iMovie. If the videos are still on your phone, you can use Live GIF ($1.99 USD) to convert it to a video file or to a GIF to send over Messages. There are other alternative apps that may be used as well that are free, such as Lively and LP. If you are looking for even more features, Live.ly may be another solution.