I can understand the confusion. Best to think of it like this, "Harp" is a static web server with built in preprocessing. "Harp Platform" is a service for running Harp apps in production.
- "Command line" - happens to be the way you access the web server.
- "Generating static assets" is just a feature of the web server.
- "Dropbox integration" is just a feature of the platform.
It's mainly between HarpJS.com and harp.io, where on HarpJS there's a command line utility that works like a static site generator, and on harp.io it's hosted. I think it works pretty well that way, just like Wordpress has a self-hosted platform as well as a hosted one.
- A command line utility for creating a preprocessing-enabled server
- A static site generator like jekyll
- A "front-end publishing platform" for Dropbox
This leads to poor understanding of exactly what "Harp" is and what it helps you accomplish.