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:


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