This version of BuddyPress should not be used on production site. It's there to ease testing for new contributors. The patch attached to the #7156 Trac ticket has been applied to ease the BP REST API import process.
From the assets section, you can alternatively:
- Download the source files if you have Node, npm and Grunt installed (don't forget to
npm install & grunt build)
- Download the packaged version
buddypress.zipwhich already includes the BP REST API.